What you see are two different backup sets. One is configured in your subscription, the other is configured server-wide. In the server security settings the option that customers can see backups that were created by an admin is active. For that reason you can see the increments, but you cannot delete them.
To stop the admin backup, login to your system as administrator, then go to the global backup configuration plan and disable that. Alternatively, simply hide the admin backups from users.