Windows Server backup - clear offline backups

Hello, 

I'm trying to count number of Windows Backup copies using my script(powershell).

Is there way, how to clear Total Backups count? I would like delete only backups on offline target. Numbers Total backups and backups avaliable should be same.

I'm able to count backup via powershell on specific target(\\?\Volume{fdcaf021-1104-4a35-a1ba-e4d16496d9eb}) but when I assign letter to this target and forget to unassing the backup target change to F:.

Thanks