The Interior Backup controls where the Blade Plunges into the Fallout (not the Matboard) on the Interior Cuts of objects.
The Interior Cut is where the Blade Plunges/Retracts from the Fallout (not the Matboard).
If the Interior Backup is cut Too Long, Decrease the Interior Backup.
If the Interior Backup is cut Too Short, Increase the Interior Backup.