The four and five digit numbers are measurements.
The 22 means 22mm wide (most common width for M.2 SSDs).
The numbers behind are the length of the plug-in module. For example, 80mm, 110mm, etc.

For the different lengths, the necessary space must be available, e.g. on the mainboard. On the other hand, the corresponding fixings must be available. The modules are usually fixed with a screw at the end of the module. For an 80mm long module, the screw must of course be in a different place than for a 110mm module. https://de.wikipedia.org/wiki...

https://dlcdnets.asus.com/pub...
On page 14/1-2 you can see with no. 6 the two M.2 slots with the different mounting options.