when U want 2 edit or assign any knob/ slider u right click it, then u choose link 2 controller,
remote control settings, **** now choose on the internal controler - Peak controller (FX ?) - Peak ... bellow it u got Mapping Formula, from the drop down menu choose inverted!

**** U only get this extra option if u've already inserted a Peak controller "plug in" in any of the mixer's channel efects slots!

Z