the one in the lower cutaway is a master volume control.

then in the usual position for controls (by the F-holes) you have a master tone control and individual volumes for each pickup. this allows you to get the balance of the volumes between the pickups exactly how you want it and then control the overall volume with the master volume control.

and of course the toggle switch is a pickup selector.
I like analogue Solid State amps that make no effort to be "tube-like", and I'm proud of it...

...A little too proud, to be honest.