Docs eating space in iCloud, Though I’m not having any big docs

Apple Support's article:

Check your iCloud storage on any device – Apple Support

tells what else may be stored in Documents:

Eg: says

?Documents (or Docs): 

Files and information stored in iCloud Drive, as well as data from other apps that aren’t listed above — for example, Notes, Reminders, Health and third-party apps. To learn about apps that can store information in iCloud, see Apps and features that use iCloud."

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More info:

How to: Manage your iCloud storage - Apple Support