It says fire 1, fire 2, fire 3 and jump which is what mousebutton 1, 2, middle and space is bound to, so I'm guessing that thats the functions that aims and fires and so on. There's 2 set-ups of those though which is wierd?
I tried to rebind both first and secondary set-ups of keybinds for both of them to mousebuttons 1-4 but that didn't help.