This is the direct statement from the Help file in TI-10. "Create differential backups" - Having chosen this parameter, check the Create a new full backup after ... parameter and specify number of differential backups, after which a new full backup will be created. The first time a full backup will be created. Next backups will be differential until the specified number of differential backups is reached. Then, again a full backup and a set of subsequent differential backups is created, then again a full backup and so on. Trouble is, this option does not appear in either Incremental or Differential Backup schemes - unless I'm missing it somewhere.