Do you have the manual? Super simple to read...
Get it here:
http://www.haascnc.com/doclib/manual/96-8000an.pdf
from the manual
Sequential Serial Number Engraving
This method is used to engrave numbers on a series of parts, with the number
being increased by one each time. The # symbol is used to select the number
of digits in the serial number. For example, G47 P1 (####), will limit the serial
number to four digits (P1 (##) will limit the serial number to two digits etc.).
The initial serial number can either be programmed or set manually. For
example,
if it is programmed, G47 P1 (1234), will set the initial serial number to
“1234.”
The initial serial number can also be set manually into a macro variable. The
Macros option does not have to be enabled to do this. Macro variable #599 is
used to hold the initial serial number to be engraved. For example, when macro
variable #599 is set to “1234,” G47 P1 (####), will produce, 1234. See the
Macros section for more information.