Why does the picture count on some people's facebook pages keep changing?

[Coco]

I noticed on someone's facebook page (ok an ex bf I am stalking, I admit it) that sometimes their picture count will say 300 and other days it will say 307. It keeps switching back and forth. I haven't noticed any new or subtracted photos. Sometimes people will have a picture count change when there are pictures their friends have put up that you can't see, but in this case it changes several times a day from those two numbers. why?

facebook glitch