The allowed movement (i.e. ONLY moving from point A to point B) is restricted to that percentage of your possible movement in that phase only... those restrictions being Snap: 20%, Normal:50% and Deliberate: 80%.
So...
you could move 20% in snap, 20% in normal and make a 60% attack in deliberate.
you could concentrate for 50% in snap and move 25% in normal (waiting to watch for other possible movement), and then the last 25% available in deliberate.
If you're doing NOTHING but moving then it's 20% in snap, 50% in normal, and the leftover 30% in deliberate (or whatever combination that totals 100% and doesn't exceed the limit for the phase).
and so on.
Basically you can move up to that amount listed each phase so long as you don't surpass your overall allowed (100%) movement for the total round.
Essentially RMSS/FRP only meters movement in a round, in order to stop the "I move from point A to point B in the blink of an eye" effect. Everything else is more or less abstracted throughout the round. (RM2 works the same way I believe while RMU does almost the exact opposite of this).