Currently there are a several digital asset trading platforms that provide investors with forms of derivative products such as futures, so one could estimate and synthesize the discrete futures curve from the averages of various curves. MVIS research used BitMEX, OKCoin, CryptoFacilities, and BTCC as sources, to construct and approximate bitcoin futures curve based on non-U.S. bitcoin futures trading on these exchanges.
Cboe Futures Exchange, LLC (CFE) launched trading in Cboe bitcoin futures at 5:00 p.m. Central Time on December 10 under the ticker symbol "XBT". XBT℠ futures are cash-settled contracts based on the Gemini's auction price for bitcoin, denominated in U.S. dollars. Gemini Trust Company, LLC (Gemini) is a digital asset exchange and custodian founded in 2014 that allows customers to buy, sell, and store digital assets such as bitcoin, and is subject to fiduciary obligations, capital reserve requirements, and banking compliance standards of the New York State Department of Financial Services.3

Although certain securities exchanges attempt to provide continuously liquid markets in which holders and writers of options can close out their positions at any time prior to the expiration of the option, no assurance can be given that a market will exist at all times for all outstanding options purchased or sold by a Fund. If an options market were to become unavailable, the Fund would be unable to realize its profits or limit its losses until the Fund could exercise options it holds, and the Fund would remain obligated until options it wrote were exercised or expired. Reasons for the absence of liquid secondary market on an exchange include the following: (i) there may be insufficient trading interest in certain options; (ii) restrictions may be imposed by an exchange on opening or closing transactions or both; (iii) trading halts, suspensions or other restrictions may be imposed with respect to particular classes or series of options; (iv) unusual or unforeseen circumstances may interrupt normal operations on an exchange; (v) the facilities of an exchange or the OCC may not at all times be adequate to handle current trading volume; or (vi) one or more exchanges could, for economic or other reasons, decide or be compelled at some future date to discontinue the trading of options (or a particular class or series of options) and those options would cease to exist, although outstanding options on that exchange that had been issued by the OCC as a result of trades on that exchange would continue to be exercisable in accordance with their terms.

The fund performance for a Geared ProShares Fund can be estimated given any set of assumptions for the factors described above. The tables on the next five pages illustrate the impact of two factors, benchmark volatility and benchmark performance, on a Geared Fund. Benchmark volatility is a statistical measure of the magnitude of fluctuations in the returns of a benchmark and is calculated as the standard deviation of the natural logarithm of one plus the benchmark return (calculated daily), multiplied by the square root of the number of trading days per year (assumed to be 252). The tables show estimated Fund returns for a number of combinations of benchmark performance and benchmark volatility over a one-year period. Assumptions used in the tables include: (a) no dividends paid with respect to securities included in the underlying benchmark; (b) no Fund expenses; and (c) borrowing/lending rates (to obtain leverage or inverse exposure) of zero percent. If Fund expenses and/or actual borrowing lending rates were reflected, the Fund’s performance would be different than shown.
•   Market Price Variance Risk — Fund shares are listed for trading on the [                    ] Exchange and can be bought and sold in the secondary market at market prices. The market price of shares will fluctuate in response to changes in the value of the Fund’s holdings, supply and demand for shares and other market factors. ProShare Advisors cannot predict whether shares will trade above, below or at a price equal to the value of the Fund’s holdings. Given the fact that shares can be created and redeemed in Creation Units, as defined below, ProShare Advisors believes that large discounts or premiums to the value of the Fund’s holdings should not be sustained. The Fund’s investment results are measured based upon the daily NAV of the Fund. Investors purchasing and selling shares in the secondary market may not experience investment results consistent with those experienced by Authorized Participants creating and redeeming directly with the Fund. To the extent that exchange specialists, market makers, Authorized Participants, or other participants are unavailable or unable to trade the Fund’s shares and/or create or redeem Creation Units, trading spreads and the resulting premium or discount on the Fund’s shares may widen and the Fund’s shares may possibly be subject to trading halts and/or delisting.

•   ETN Risk — The Fund is likely to obtain substantial exposure to the price movements of bitcoin by holding ETNs that provide exposure to the price of bitcoin. ETNs are unsecured, unsubordinated debt securities of an issuer that are listed and traded on a U.S. stock exchange. An ETN’s returns are generally linked to the performance of a particular market benchmark or strategy minus applicable fees. ETNs do not provide principal protection and may or may not make periodic coupon payments. ETNs are subject to credit risk, which is the risk that the issuer cannot pay interest or repay principal when it is due. Additionally, the value of an ETN may be influenced by time to maturity, level of supply and demand, volatility and lack of liquidity in the underlying market (e.g., the commodities market), changes in interest rates or the issuer’s credit rating, and other economic, legal, political or geographic events. The value of an investment in an ETN may be impacted by fees associated with the ETN. Structural aspects of the ETNs may impact their market value. Trading by affiliates of an ETN sponsor may create conflicts of interest. The issuer of an ETN may be unable to meet its obligations. The potential impact of Bitcoin Network forks on the value of a bitcoin ETN is unclear. ETNs issued by special purpose vehicles may include greater risk. ETNs are subject to risks associated with the underlying asset.

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.
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