•   Futures Position Limit Risk — Limits on the amount of futures any one entity can hold may negatively impact the Fund’s ability to meet its investment objective if such limits are reached and exceptions to such limits are not granted. Currently the position limits for bitcoin futures contracts are much lower than they are for most other futures contracts.

Source: MV Index Solutions GmbH (MVIS®). MVIS is a wholly owned subsidiary of Van Eck Associates Corporation. Data as of December 8, 2017 (synthesized data from BitMEX, OKCoin, CryptoFacilities, and BTCC which represents non-U.S. listed bitcoin futures trading on these exchanges). Not intended to be a forecast of future events, a guarantee of future results or investment advice. Current market conditions may not continue.  

There's a lot of ins and outs which can get confusing in arbitrage trading. We won't go into the technicals of why futures contracts trade at a premium to spot price. You can read a full explanation here. If it's not of interest to you, all you need to know is that there's a tendency, the further out in time the futures contract expires, for the premium to spot to be higher and higher in nominal percentage terms.