I think this happen because this installation is an upgrade, so the user have some videos that not properly deleted.

I have created another test account and uploaded video, number is showing properly.
i just created my own account and it still happends, try adding a video then deleteing it...then adding it back to the same user, then delete again. It happends as when the user removes a video it decreases there video count by 1 but when a video gets added to a user from the admin pannel it does not increase the video count or space.

P.S why is BBcode off for users on the forum?