The V-Groove Interior Backup controls where the Blade Plunges into the Fallout (not the Matboard) on the Interior cuts on the Inside Cut of the V-Groove. The Interior Cut is where the Blade Plunges or Retracts from the Fallout (not the Matboard). If the Interior Backup on the Inside Cut of the V-Groove is cut Too Long, Decrease the Interior Backup. If the Interior Backup on the Inside Cut of the V-Groove is cut Too Short, Increase the Interior Backup. The V-Groove Interior Backup field is marked with a Black Arrow on the Configuration screen and the Map illustration.  See: V-Groove Interior Backup Configurations | 
