A Riddle.

A man wanted to enter a club. the entry of the members was with a password. the man hid besides the wall and tried to overhear the password. A member came and the guard said 12', and the member replied '6'. the watchmen let him in .Another member came and the guard said '6', and the member replied '3' and he was also let in. the man deduced that the password is the half the number recited by the guard. he went confidently and the guard said '8' and the man replied '4'. and the guard didn't open the door for him.

what was the PASSWORD?