My E-M1X had 242 clicks on it when I received it on the first day it was available.In the Olympus naming scheme, the first letter is typically 'P', but you can change it in the menus. On each of my Olympus cameras since they have added the mechanism, I use a different letter (i.e. my E-m1 mark I is 'W', my E-m10 mark II is 'X'). See page 120.
The second letter denotes the month ('1' for January, '9' for September, 'A' for October, etc.).
The third and fourth letters denote the day of the month (i.e. July 18th in your example).
The last 4 letters are the file number. You can select whether file numbers are retained from previous cards or reset when you insert a new card. See page 120. When the file number reaches 9999, the next file creates a new directory (i.e. DCIM\101OLYMP instead of DCIM\100OLYMP) and puts the new files in that directory.
I would imagine the factory does some tests that bumps up the file number if you bought it new. And brick & mortar stores have been known to allow people to try out the camera before buying it, and that could also increase the file number.