Norton Ghost 15.0 Cannot change the number in the "Limit file versions for backup storage"

Hello.

 

We are using Norton Ghost 15.00. I unchecked the "Limit file versions for file and folder backups" box, but the number of versions remains grey and I am unable to change the number of versions, which is presently set to 6.

 

The size of the disk is 75GBs, yet the size of the backup file folder is 418GBs!!!!!!!!!

 

What's wrong here. Why am I unable to change the number of file versions for file and folder backups?

 

Thanks

 

Mike