The input decides where center is; pan it half left and it is half left.
From there you have more left than right going into the reverb.
The width narrows how much wider that reverb is.

If you want 'exact' control a reverb routed out to (presumably) hardware and recorded back as separate tracks via a mixer could be panned exactly where you want, if you could record the resulting stereo reverb signal as 2 separate MONO tracks and control them in the mix later.


It's much like panning a stereo piano sample to still have some L/R feel, but be mainly on the right side of the stage. It's much easier using two separate L/R channels and panning those to the width you desire.


I do not work here, but the benefits are still awesome
Make your sound your own!