If you delete an already backed up file from your ReadyNAS it will not be deleted from your Account. We believe that a backup solution should not delete files just because you deleted them from your local computer either accidentally or on purpose. We keep all files, which also allows you to use our system for storage as you freeup local disk space. This compares to systems that simply "mirror" your current system.
The only way a file will be deleted from your Account is if you manually deleted it using our software tools.