Enjoyable but runs up storage space

I really like using this app but when you use it, and optimizing performance box appears while youre trying to play it, which uses up storage space on the phone, especially after you have already worked so hard to get it cleared up. Please fix this. It needs to be changed so that whatever storage space gets used up from the performance optimization immediately gets restored when the app is closed.

Morgan Douglas about GarageBand, v2.1.2