phantom iCloud back up

Hi

I have a problem with iCloud and iPhone backup. I have many devices but I back up only my iphone and some apps. If I go to iCloud.com to check the status of iCloud space it says there is a backup of more than 1GB, while my only device is around 500 MB.

iCloud.com says 2GB out of 5GB are taken for back up and data, but it should be 1GB.

It might be useful to know that I noticed this issue after I installed the beta 9 on the iphone and reverted to iOS 8

Do you know how I can fix this?

Thank you

Emanuele