The pin switch on the face bottom left side in GND is in all metal mode,when up in disc is in discrimination mode, both those positions the metal detector has to be in motion. Once the trigger switch on bottom of detector is held in the detector is in non- motion modes in GND and disc modes. The switch on bottom is not the pin switch on face. To ground balance
set knob to 12:00, set pin switch to GND. Hold trigger-switch on bottom on, lower coil and hear if it goes lower or higher, adjust as needed.
So the pin switch on face with GND is a 4 mode switch, 2 motion, 2 non motion.