Backup size don’t match actual

i keep getting a message about not having enough iCloud storage so I thought I do a test Turned off and deleted my iCloud backup, size is now zero. I turned it back on and only have Facebook on for backup which is 136 MB in size. After backup is completed, it is saying I have 4.22 GB backed up and another +33 MB addition on my next backup. This is fishy to me, sounds like iCloud + marketing is fidgeting with the IOS firmware to get me to buy more storage.