Reducing space of iCloud-Backup

Apple’s iCloud-Backup often uses more space than needed.
Follow the steps below to reduce space.

1 1.9 GB available at initial state
2 Delete iCloud-Backup
3 Create a new backup
4 2.2 GB available at final state


I could reproduce this behaviour frequently using iPad and iPhone with iOS 6.
In all cases no settings of iCloud-Backup (activate/deactivate backup of app-data) have been changed and no apps have been used.