The Cut Preview will display a Vertical or Horizontal line where it will trim off the remaining matboard if a Remnant Directionis selected under the Advanced Outside Options.
Select the Remnant Direction to Off to turn off this feature and the Cut Preview will no longer display nor cut the remnant from the outside of the mat.
Remnant Trimming feature trims off the remaining portion of the mat Horizontally or Vertically after cutting the design to make storing the leftovers easier.