How to delete app data from iCloud?
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What you are seeing in that image is what is backed up in iCloud. You have to delete the app on iPhone by holding down its icon and then pressing the cross which appears when the icons start wiggling.

Then you'd be able to delete its data from iCloud by going to iPhone settings-> Account (First in the list with your name and photo)-> iCloud-> Manage Storage-> Ulysses classic-> Delete documents and data.