Spotify App needs more storage space AFTER un-downloading songs

[zaps]

Plan

Free/Premium

Country

Austria

Device

iPhone 6S

Operating System

iOS 12.0.1

My Question or Issue

When making multiple songs available offline the storage use naturally goes up. (And by the way, after having that issue for YEARS there STILL is no functionality to clear the cache ... we still need to reinstall the entire app)

My phone is now on storage limits. The strange thing is that when I uncheck the "Download" switch the disk space use goes UP instead of down. Can anyone explain that behavior?

[zaps]

Forget my complain about the clear cache button, it is already in app. Thanks for that and sorry!

Nevertheless, it would still be good to know why storage goes up after I uncheck that switch.