Thanks for the link. I'm not sure that explains everything that's happening here though. If you want to recreate the issue or see what I'm using, I'm using the bookmark list filter to get data from my Olio Portfolio list (BMA4Q0D).
Here's a couple of examples of the inconsistencies I'm seeing:
For GC8ZGTK, PGC Top most image logs returns 30, but according to GC.com's gallery, there's only 28 pictures.
For GC8ZV2Q, PGC says 9 but GC says 8.
For GC8ZME1, PGC says 6 but GC says only 5.
Where is ProjectGC getting these extra pictures from? The rest of the differences seem to be explained by the FAQ (ie. there were images I uploaded to use in the cache description).