I image you are seeing what should be expected as the appliance is reflecting what VMware defines as the provisioned space. Basically it is showing you the properties of the disk. However, the backup is only backing up used space during a full (I think), and changes during incremental backups. And as Chris Huff points out, de-duplication will cut that utilized space way back as only the unique blocks are actually retained.
My file server is thick provisioned 2TB, and is shown in the restore browser as such, but only a small fraction of space is taken on the backup appliance.Go to the full post