Unclamped, in 8-bit (and PrPro is always 0-255) ... the whole scale of the say RGB Parade scope jumps.
The bottom "0" line will be down near the bottom of the scope area one instant, then pop up 20% or more up ... then down ... then even higher ... then partially down ... then to the bottom ... then way up again ... on and on.
Clamped, the 0 and 100 reticules go to the very bottom/top of the scope window, and naturally stay there.
As I've told the engineers at NAB, I'd prefer the "unclamped" action be to move the reticules away from the edges, and let the media fly around as it may. The main reason I use "unclamped" is to see the media trace that may be beyond the clamped 0-100 scale area. I can do that just fine without the scale itself hopping all over.
Neil