If you take a look at the 1st page of this thread User Tjeli explains the settings pretty good. 1-3 are gain, 4 is remote on, 5 is crossover on\off and 6 is crossover adjustment.
I tried raising the gain switches but it was too loud for me even with the control knob. The knob works but I don't like having to make big adjustments all the time. Mine came set up with switch 1,4,5 & 6 up. 2 & 3 are down.