I think what you are refering to is Delta Peak value, from what i understand your battery's will increase in voltage as you charge and then decrease as they peak out , the settings in the charger are in 0.3 milivolt per cell the higher the value the more you will cook your packs !! I generally run at 0.3 for all my NIMH packs .
I have run up to 0.5 on some older packs that were false peaking.
I am mainly charging reciever packs so there is bound to be better settings for race packs