Holley stumble trouble

Any idea how wide the sweep is? What I mean is if the screw is backed all the way out, at what rpm does it begin to move? What if it’s cranked in the whole way? Does that disable the advance or what rpm is now required to activate it?
Most that I have played with dont even start to move until they get 15 inches.
I searched a long time before I found one that triggers at 8.5 inches
Have not tried it yet.