Ghost 10 Recovery Point Issue

In trying to defragment, I got this message: Volume Backup has 0% free space available.

The system suggests that I delete unnneeded files. But the only files on the Backup drive are Recovery Points. In the Recovery panel, when I click on Optimize Recovery Point Storage, I get a dialog box with one "group" of 21 recovery points listed.

If I click in the checkbox for that one group and then on the Delete button, the system presents the message:  You have chosen to delete all of the recovery points. You will no longer be protected.

 

How do I get around this? I'm willing to delete some recovery points, but I'd rather not delete all just before a defrag.

And, how can I set the system up so this doesn't happen again?