Minimum of 630? So someone went through each picture and tallied a total of at least 630 individual.. erm... foofs.
That's a very weird job, how to you even phrase that on a CV?
Forensic photographic lingerie analyst?
Either that or they used similar software to what they use for matching other dodgy pictures on the web with what is found on suspects machines, so they load the pictures in and it works out how many unique ones there are and how many close matches.
Which would explain why you might get a result of "at least 630" as the software might have 630 definitely unique images with no close matches.