Siemens SINUMERIK 840Di Function Manual page 744

Detailed Description
2.1 Axes
Fig. 2-4
Note
Leading zeroes in user-defined axis identifiers are ignored.
Example:
MD10000 AXCONF_MACHAX_NAME_TAB[0] = X01 is equivalent to X1
The geometry axes must be assigned to the channel axes in ascending order leaving no
gaps.
2-14
Axis configuration
Axis Types, Coordinate Systems, Frames (K2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0