Kobo images sub folder names on device

[Twombs]

Hello folks. I was wondering if anyone reading this knows how the two sub-folder names inside the .kobo-images folder are determined?

i.e. G:\.kobo-images\0\20\da2dc827-1e33-472e-b764-4014f10ffa10 - N3_LIBRARY_FULL.parsed

This would be the '0' and '20' sub-folders in the above path. The .parsed file is actually a .jpg file, and each folder with a full complement has three such files, all different sizes for different views on a Kobo device. There are many different number sub-folders, but a combo of two in every instance. That '0' sub-folder might have more than the '20' sub-folder in it, as sometimes there are several number sub-folders within the first number folder.

I have investigated the KoboReader.sqlite file, and can find no mention of them, so I am guessing some kind of formula or method is at play.

I need this information, because I have started developing a program to fix the missing cover images that occur regularly on my device, and Kobo's flawed Repair option only fixes them temporarily ... when it actually works. A sync or so later, and some are missing again.

My project can be found here - https://www.autoitscript.com/forum/topic/210281-kobo-cover-fixer