Note about my values:
In my math, if you extract 96-128, what I would expect to happen is that it starts at 0 at 96 an then reaches 1 at 127 and then stays at 1 until the end.
It sounds like what you want is to actually have it switch to black after saturating the 1? fwiw in that case, it doesn’t mean what I suggested is wrong, just you want to do something different.
Normally the fact that it stays at 1 above the target is not a problem since when you stagger the blends in order, they always draw over the clamped white part.