OK, here it is:
There are a number of things the voltage curve does on charge. As the cell reaches full charge the rate of change of the voltage goes from positive to negative. That is it was increasing more and more and then the rate of increase starts to drop off. The point where the rate of change goes from positive to negative would be the zero peak. If you are mathematical it is easier to state this. The zero peak is when the second derivative of the voltage curve = zero, that instant when it goes from positive to negative. The other, negative delta peak is when the voltage peaks and then starts to drop. The sensitivity setting is how much of a drop or change or how fine do you detect the zero point to terminate the charge. In either case the sensitivity settings are essentially the same.