I know from experience of playing this game how the counter factor makes him go over his target, I just wasnt sure which counter factor was best, thats all
You will have to play with it on your system, 6 will probably be best for you. Games run different on different specs. My system is 1/3 the speed of yours, so it will be totally different for you than me probably.
Keep your counter factors as they are programmed unless you know exactly what you are doing. Counter Factor is one of the advanced contorls in emulating N64 games, messing it up might screw up a games timing. DK64 you might have to adjust it in parts of the game (IE. Barell shooting)
If you want to know what it means and what it does, read the 1964 helpfile which is handily included in every single download of the emulator It's a good read, honestly.