It is a 7 bit number between 0 and 127 sent thus:

G130 X127 Y127 A127 B127 for full power

G130 X0 Y0 A0 B0 for no power

Be careful or you will lose steps if you reduce it. You cannot print as fast with it set to a lower number and if you set it to zero while something else happens then it is possible for the filament to rotate the extruder stepper or the umbilical to move the head.