This method only backup the changed and newly added files based on the last backup, be it a full or incremental backup. The data that have not been changed will not be backed up. All the image files of incremental backup share a close relationship. If any one of the incremental image files has been damaged or missing, the latter image files will be invalid.
You can still directly start an incremental backup for a backup image from the Backup and recovery page by clicking Backup --> Incremental backup.