I deleted movie projects within Imovie but it didn't open any storage space

I was reading some discussion about how some projects/files stay on a mac until they are deleted in a certain way, but curious how that applies to an iphone. I tried deleting many of the movie projects that I have in iMovie, but it shows that there hasn't been any drop in storage space for my iMovie app.

How do I free up space in this area? Thanks for any help!