DO NOT TURN THE SET SCREW WITH THE BALLS! That is to keep the clutch at a set "ride height" (for want of a better term). Once you get it set, leave it be.
All clutch adjustments are always via a tension adjustment (even, in a way, a centax). In this clutch's case, it is via a spring.
Tighten the "preload" on the spring, make it need higher revolutions to spin the shoe out and therefore it shifts later.
Loosen the "preload" on the spring, make it not need as many revs to spin the shoe out and therefore it shifts sooner.
This is what the directions say. If you follow them (I don't remember what the initial settings are) you should have a decent base to start with.
However - if you aren't sure it's shifting (and I was in this boat) then tighten it a bit and see if it acts differently. Make sure you're in first gear - by tightening the adjustment screws (equally).
Then, using 1hr increments, slowly back it out until it does start shifting. Then you can adjust it.
Small adjustments work quite well.
RC10L2.5W - RC12.4 - RCNTC3(bmi) - TC4 (modded) - B44.2 - plus rent-a-rides! :D