Exchanges simply take a fee to facilitate the orderbook where its clients (the counterparties) create and trade futures contract with each other. They also have to manage the system's risk so that traders don't get overleveraged or manipulate the market. Since counterparties are only putting margin down that is a % of the contract value, the exchange also has to handle liquidation procedures in case the value of the margin is exceeded by the loss on the notional market value of the contract. For instance, BitMEX offers 100x leverage, so if you want to enter a $10,000 position you need to put down $100 worth of bitcoin. If the price moves just 0.5% against your favor, BitMEX will take over your position and execute it into the market, so that the person on the other side of the contract can have someone else who pays for the profit. In the event that the liquidation doesn't get passed off to another trader, an Auto-Deleveraging/Termination can occur, or Socialize Loss in the contract builds (we will discuss these issues in more detail later).
If the Funds engage in offsetting transactions, the Funds will incur a gain or loss, to the extent that there has been movement in forward currency contract prices. If forward prices go down during the period between the date a Fund enters into a forward currency contract for the sale of a currency and the date it enters into an offsetting contract for the purchase of the currency, the Fund will realize a gain to the extent that the price of the currency it has agreed to sell exceeds the price of the currency it has agreed to buy. If forward prices go up, the Fund will suffer a loss to the extent the price of the currency it has agreed to buy exceeds the price of the currency it has agreed to sell.
The Trust reserves the absolute right to reject a purchase order transmitted to it by the Distributor in respect of any Fund if (a) the purchaser or group of purchasers, upon obtaining the Shares ordered, would own 80% or more of the currently outstanding Shares of any Fund; (b) the Deposit Securities delivered are not as specified by ProShare Advisors and ProShare Advisors has not consented to acceptance of an in-kind deposit that varies from the designated Deposit Securities; (c) acceptance of the purchase transaction order would have certain adverse tax consequences to the Fund; (d) the acceptance of the purchase transaction order would, in the opinion of counsel, be unlawful; (e) the acceptance of the purchase order transaction would otherwise, in the discretion of the Trust or ProShare Advisors, have an adverse effect on the Trust or the rights of beneficial owners; (f) the value of a Cash Purchase Amount, or the value of the Balancing Amount to accompany an in-kind deposit, exceeds a purchase authorization limit extended to an Authorized Participant by the Custodian and the Authorized Participant has not deposited an amount in excess of such purchase authorization with the Custodian prior to the relevant cut-off time for the Fund on the transmittal date; or (g) in the event that circumstances outside the control of the Trust, the Distributor and ProShare Advisors make it impractical to process purchase orders. The Trust shall notify a prospective purchaser of its rejection of the order of such person. The Trust and the Distributor are under no duty, however, to give notification of any defects or irregularities in the delivery of purchase transaction orders nor shall either of them incur any liability for the failure to give any such notification.
Here you will learn more broad concepts regarding daytrading bitcoin and futures in general. Even if you are not an active trader, there's a lot to learn about markets and how they're structured in this guide.  Some of the early sections may be a little too easy for those of you who already are traders, so just navigate through to the part that is most relevant to you if you want to hit a more advanced topic in the guide.
The Fund pays transaction costs, such as commissions, when it buys and sells securities (including through the Subsidiary, as defined below) or “turns over” its portfolio. A higher portfolio turnover rate for the Fund or the Subsidiary may indicate higher transaction costs and may result in higher taxes when the Fund’s shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the example above, affect the Fund’s performance. The Fund has not yet commenced operations as of the date of this Prospectus. Thus, no portfolio turnover information is provided for this Fund.

Jordan Kelley, founder of Robocoin, launched the first bitcoin ATM in the United States on 20 February 2014. The kiosk installed in Austin, Texas is similar to bank ATMs but has scanners to read government-issued identification such as a driver's license or a passport to confirm users' identities.[60] By September 2017, 1,574 bitcoin ATMs had been installed around the world with an average fee of 9.05%. An average of 3 bitcoin ATMs were being installed per day in September 2017.[61]
Each Independent Trustee is paid a $185,000 annual retainer for service as Trustee on the Board and for service as Trustee for other funds in the Fund Complex, $10,000 for attendance at each quarterly in-person meeting of the Board of Trustees, $3,000 for attendance at each special meeting of the Board of Trustees, and $3,000 for attendance at telephonic meetings. Trustees who are also Officers or affiliated persons receive no remuneration from the Trust for their services as Trustees. The Officers, other than the CCO, receive no compensation directly from the Trust for performing the duties of their offices.
Futures contracts expire on a designated date, referred to as the “expiration date.” Each Fund typically will invest in “lead month” contracts. Lead month contracts are the monthly contracts with the earliest expiration date. Bitcoin futures contracts listed on the CBOE Futures Exchange (“CFE”) or Chicago Mercantile Exchange (“CME”) will be cash settled on their expiration date unless they are “rolled” prior to expiration. Each Fund generally intends to “roll” its bitcoin futures contracts prior to expiration to the next “nearby” bitcoin futures contract. The “nearby” contracts are those contracts with the next closest expiration date. The Funds will incur the costs (or benefits) of continually rolling into the new lead month contracts.
•   Non-Diversification Risk — The Fund is classified as “non-diversified” under the 1940 Act, and has the ability to invest a relatively high percentage of its assets in the securities of a small number of issuers susceptible to a single economic, political or regulatory event, or in financial instruments with a single counterparty or a few counterparties. This may increase the Fund’s volatility and cause performance of a relatively smaller number of issuers or the credit of one or a relatively smaller number of counterparties to have a greater impact on the Fund’s performance. This risk may be particularly acute if the Fund is comprised of a small number of securities. Notwithstanding the Fund’s status as a “non-diversified” investment company under the 1940 Act, the Fund intends to qualify as a “regulated investment company” accorded special tax treatment under the Internal Revenue Code, which imposes its own diversification requirements that are less restrictive than the requirements applicable to “diversified” investment companies under the 1940 Act.
In 1998, Wei Dai published a description of "b-money", an anonymous, distributed electronic cash system.[14] Shortly thereafter, Nick Szabo created "bit gold".[15] Like bitcoin and other cryptocurrencies that would follow it, bit gold (not to be confused with the later gold-based exchange, BitGold) was an electronic currency system which required users to complete a proof of work function with solutions being cryptographically put together and published. A currency system based on a reusable proof of work was later created by Hal Finney who followed the work of Dai and Szabo.
Since you bought 68.4246 BTC, you want to short 68 BTC and lock in the USD value. You will have 0.4246 BTC left over, which will give you a slightly long bias. You can either fix this by only buying 68 BTC in step 1 or by giving yourself more short exposure by shorting 69 BTC. Remember that CryptoFacilities contracts are inverse (which allow locking in USD) and are denominated in BTC