all you need to do is this :-
Rapid to the center + the circle radius + or - the radius of the cutter e.g.
G20 G40
(1/2" dia cutter and 3" hole centered around X0 Y0)
G00 G90 X1.25 (1.5-.25) Y0 Z1.
Z.05
G01 Z-1. F10.
G02 I-1.25
G00 Z1.
(Then a 1/2" cutter and a 4" boss centered around X0 Y0)
G00 X2.25 (2.0+.25) Y0 Z1.
Z.05
G01 Z-1. F10.
G02 I-2.25
G00 Z1.
M30