Hey Russel,
these are work offset coordinate systems. By default the G54 system is active. If you program a second coordinate system by entering offset values and switch to it with G55, you can run the same program at a different location on your waste board. You could have a number of fences with blanks on them on your wasteboard and with these offset coordinate systems, you could apply the same program on them, one by one.
The values are usually available in parameters #5221 – #5386, and the currently ative coordinate system is stored in parameter #5220, but on the Masso, it seems the support of RS274/NGC G-code is incomplete.
– Source: NIST RS274NGC language (G-code)