The controls are simple, but they work very differently from those of most other pedals.
The "Sensitivity" control is used to adjust the amount of incoming signal. You can almost think of it as a Pre-amp control. The higher the sensitivity control is turned up, equals more guitar signal reaching the distortion generator. In some modes this control is best used turned way down to help control the octave "flipping" that can occur at higher gains.
The "Boost" switch will add an extra 15db worth of gain to the overall signal going into the octaver circuit. This will give the pedal a real "smash in the face" attitude to the sound, and when used in the "octave off" mode, the boost will produce some serious wicked distortion.
The "Octave Off" switch takes the octave divider out of the circuit, but not completely as that circuit also creates a great deal of the boxes distortion, some octave bleed through is normal.
The "Output" control is just what it says; it controls how much signal leaves the pedal.