I've been slapping another player in the 1900s over several days, and countering, and he's been attacking me and eating my counters. Then, today, he attacks me and I go to set up a counter and get this: "[Player X] has 5 attack(s) on you (In 8 hours). You have 52 attack(s) on [Player X] (In 4 days). Please see Rivals Help for further information on counter attacks." How did that happen? How come all his attacks have vanished, but all mine are recorded?
Counter attacks also count as an attack against your opponent. Also, your attacks against count will continue to increase if you don't allow for a rest period of 24 hours (no attacks) against that target. It is possible he waited 24 hours without attacking you.