Hmmm... Just about every possible conflicting answer...
My dealer doesn't know either.
I wonder if I could find out through KYB?
After re-valving shocks for various vehicles for many years I've found for a particular spring rate and vehicle/rider weight there is an ideal setup for low speed compression, low speed rebound, and high speed rebound. Where I've found it hard to find an ideal setup is the high speed compression damping (a little softer - but still highly damped is ideal for aggressive trail riding, and very high high speed damping is ideal for landing off jumps).
So, in my dream world, the knob would largly control high speed compression damping and the other rates would be ideal for a 250 lbs (including gear) aggressive rider, who also wants a smooth ride at lower speeds.
The shock is rebuildable, so I can probably tweak it pretty close to what I want - if aftermarket valve parts are available...
Steve