Running out of space over photo issue

My daughter has a 16gb iPad mini. She is reaching her mas space and we wanted to remove some of her photo's videos etc.....to create more space. Well if I go to settings, general, about, it says there are slightly over 700 photos. But when I go to the photo app and click the photo tab which shows all the photos it only shows slightly more then 400, where are the other 300? Is it possible duplicates are stored somewhere?

I was just looking at my "Photo Stream" tab in the App and found some old photo's that don't show up in the photos tab. It does allow you to edit and delete them, not exactly sure why they are there??

I don't believe another app can contain photo's.