I don't have VDR running, so you may need to check the manual for details. Anyway, any backup application which offers incremental (or differential) backups internally maintains the necessary information about the backup chain (e.g. full -> inc1 -> inc2 -> inc3). If you need to restore a file, the backup software is aware of the location of this file and you won't have to know in which incremental or full backup the latest changes of this file are stored.
André