You can delete videos from your library as a way of keeping things organized. The hours still count against your plan, they cannot be reused.
To delete video, go to your Video Library and select the specific video to continue to the Video Player page.
The select the Video Menu on the left and click on "View / Edit Details".
Click the Delete button midway down the page.
Confirm that you want to delete the file.
Once you confirm by hitting OK, the video will be removed from your team's video library.