How are you supposed to go about progressive overload with this protocol? Do you try to do more reps for example:
9-12 + 3 + 3 + 3 + 2 ( and try to get 3 on this set )
then continue to add a set when you can get 3 on your previous set.
Or do you increase the weight a bit
9-12 +3 + 3 + 3 + 3 ( new PR on last set so next time you increase weight ).