Your opponent is a premium member and is getting placed on auto-vacation. When that happens, 24 hours automatically gets deducted from their vacation bank.
If the player comes off vacation before that time has elapsed, the difference gets added to their games where they were on vacation, up to the max time control.
I am playing in Chess Masters. (http://www.chess.com/tournament/chess-masters8)
My opponent, Victimised, has not moved against me for days. He keeps going on vacation, which I am not questioning. I am, however, questioning something else; when I last checked he had 36 minutes to make his move (after coming off of vacation). Now he has 14 hours.
How does that work?