G83 question

I am trying to use G83 to drill a hole. The surface of the material is -4.5538. I want to drill the hole 0.750 deep.
I don't understand what the settings of Z and R should be. I tried G83 X0 Y-0.625 Z-0.750 R0.2 L1 Q0.05 and it retracts Z to 0.2 (way above the material) and starts drilling air. I don't really want to break a drill bit, so should the code be:
G0 Z-4.0538
G83 X0.0 Y-0.625 Z[-4.5538-0.750] R[-4.5538+0.2] L1 Q0.05
Y0.625
G0 Z-4.0538


Thanks in Advance,
Alan