Hey guys,
I'll ask the team to provide an answer (likely not until tomorrow), but it's also possible that the number represents images that were approved ever. If an image was subsequently removed by the user, or rejected for a trademark or some other reason during a regular audit, you would have less active images being sold.
I'm speculating; I'll clarify with the developers that built the functionality. I suspect it could also be the issue mentioned earlier, which is that some images were recently approved, but haven't been indexed for search yet.
Best,
Scott
VP of Content