Storage data not adding up

When I go into iTunes, I see that there is a total of about 9 gigabytes in video despite only having 8 or so videos downloaded. On my iPhone it says that there are only 3 gigs of videos, however, it still says that there is 25 total gigs on the device. This doesn't add up with all the data, so the extra 6 or so gigs has to be coming from videos. How do i fix this?