The Exterior Backup controls where the Blade Plunges into the Matboard (not the Fallout) on the Exterior cuts of Openings. The initial plunge position is determined by the bevel type.
The Exterior Cut is where the Blade Plunges or Retracts from the Matboard (not the Fallout).
If the Exterior Backup is leaving a Hook in the corner, Increase the Exterior Backup.
If the Exterior Backup is cut Too Long, Decrease the Exterior Backup.
If the Exterior Backup is cut Too Short, Increase the Exterior Backup.
The Exterior Backup field is marked with a Green Arrow on the Configuration screen and the Map illustration.
See: Exterior Backup for Openings Configurations