1. rapid height should not be at 0.0, that would leave a line where the drill marks the surface when traveling from hole to hole.
2. 5 inches downward would make it Z-5.0. On most machines, (and i think its better this way) when your tool moves into your material, regardless of what is moving (spindle or table) the move is negative, if the material is moving away from the tool, then the move is possitive.
So your line of code should turn out to be like this:
N45 G81 X0.4771 Y1.1648 Z-0.5000 R0.1000 F3.00
So R=0.1 is greater than Z=-0.5
This code will drill a hole at X=0.4771 and Y=1.1648, at a depth of 0.5 inches (z=-0.5), at a feed of 3 inches per minute, when the hole is done, the tool will rapid back at 0.1 over the material. and will be ready to rapid to another hole location. (all this providing the Z movement is negative when the tool goes into the material)
Hope that helps
Regards
Fernando