Have another read of the help files.
look under "Share media".
When you choose to export to iTunes, if you look carefully you will see it says "Share PROJECT to iTunes".
YOu will then find the project file under the apps, Sharing tab in iTunes.
The file it creates is an iMovie mobile project file, intended to be opened in iMovie Mac.
If you want to export a video, then export to the camera roll as a video, and import as you would any other video on your iPad or iPhone.
When you export to camer roll it makes a QuickTime (.mov) file.
This can be imported to your computer as you would import photos; via image capture, iPhoto, or start menu-portable device-import pictures and video.
You should not be using iTunes to import video.
I think you are seeing the old project file you exported before.
imovie does export as video files, and once they are on your computer you will need to buy DVD authoring software to convert this video to a DVD if that is what you are after.
So please do go back to the help page I suggest earlier and read it.
It says everything I wrote here.