Parameter #5203 ?

Does anyone know what parameter #5203 is? I am looking at the following line in probe_z_minus_wco.ngc

#<workspace_z> = #[5203 + [20 * #5220]]

#5203 is not in the reference and would fall between these.

5211-5219 - "G92" offset for X, Y, Z, A, B, C, U, V & W. Persistent.
5210 - 1 if "G92" offset is currently applied, 0 otherwise. Persistent.

I would guess then it is being used as a temporary variable.

I did a grep through all of the macros and it is always used but never set. Ahhh but the light just went on. It is just a reference starting point. Say we are in G55 then #5220 would equal 2. (20 * 2) = 40. (5203 + 40) = 5243 which would be the Z location in G55.

5241-5250 - Coordinate System 2, G55 for X, Y, Z, A, B, C, U, V, W & R. Persistent.

probe_cal_round_boss.ngc: #<workspace_z> = #[5203 + [20 * #5220]]
probe_cal_square_boss.ngc: #<workspace_z> = #[5203 + [20 * #5220]]
probe_rect_boss.ngc: #<workspace_z> = #[5203 + [20 * #5220]]
probe_ridge_x.ngc: #<workspace_z> = #[5203 + [20 * #5220]]
probe_ridge_y.ngc: #<workspace_z> = #[5203 + [20 * #5220]]
probe_round_boss.ngc: #<workspace_z> = #[5203 + [20 * #5220]]
probe_z_minus_sub.ngc: #<workspace_z> = #[5203 + [20 * #5220]]
probe_z_minus_wco.ngc: #<workspace_z> = #[5203 + [20 * #5220]]

Thanks you