Backup of iMovie

If I make changes to a clip in the time line in iMovie, does time machine just make changes in the individual clip in the package or does it backup the whle package even though only a single change was made? If the whole package, do you have any suggestions on how to run sensible backups, so I don't run out of space on my backup hard drive. I have over a hundred movies, and I am constantly making minor edits to my movies.