50 bodog fullring

EP raises 3 blinds, i call in MP with 22.

flop is AQ6, EP checks, i bet 3/4 pot, EP calls.

turn is 8, check check.

river is 2, no flush, EP bets about 1/3-1/4 of pot (i read as a value bet, probably a pair, possibly top), pot is 13$ and we have 40$ stacks, how much do i raise?

P.S. this may be kind've a silly question, but im asking because i have very little experience with massively overbetting for value.