In Documents, here's how the space the app takes up is counted in iOS settings: the size of the app itself (like when you initially download it from the App store) + all the files you see in your iCloud Drive > Locations > Documents + files from iTunes Files folder + different cache types (you can check them in iExplorer).
If you notice that the app starts occupying too much space on your device and it seems to be unrealistic, please proceed as follows:
- Make sure there are no files in the Recently Deleted folder.
- Fully close the app.
- Restart your iPhone or iPad.
- Wait a few days until the cache is cleared.
Usually, it’s actually the cache taking up that much space.
Please keep your eye on the matter and in case the cache is not cleared, drop us a line at firstname.lastname@example.org - we're happy to help you personally.