"The future flight credit will be listed online as a canceled flight. The new booking has to be in the same name as the previous booking but if the future booking is cheaper (and not originally booked after 2 March 2020) you will receive an ETC for the difference."- - -
My experience using
UA Future Flight Credit is that you
MUST buy a new ticket of equal or greater value or you
lose the residual value of the Future Flight Credit. :-(