I think itās a semantic problem.
VOL is probably output volume of DRY (uncompressed) sound.
Make up gain and compressor output are the same thing. the only difference that usually, make up gain is scaled differently.
Yeah, by playing around with it I confirmed this.
The VOL is dealing with DRY uncompressed sound.
You can tell because when you lower it all the way, the compressor is still compressing. You cannot hear anything because the compressor output is down.
The output is really just an ATTENUATOR where 127 is Unity gain.
Itās also can be used to further refine how much dry signal is fed into the Mix knob. So ultimately, itās just one more control to use when setting up gain.
Itās confusing a little but itās definitely not reacting with the compressor.