Example:

Hypothetically, if bitcoin investment typically yielded returns of 1 % a year (not necessarily an accurate number, but chose for purpose of simplicity), than 1 bitcoin in hand would be worth 1 bitcoin (present value calculation for money in hand is rather easy to calculate).  Present value of 1 bitcoin which has been held in hand one year ago would be 1 bitcoin, plus 1% of one bitcoin.  Present value of 1 bitcoin to be received in one year would be 1 bitcoin, minus 1% of one bitcoin.