Troubleshooting to Calculate Opening Adjustments

Cut a one layer rectangle opening. 

From the front of the mat, measure the Width and Height of the opening from the inside of the bevel. 

Enter those values into the Actual Height and Actual Width fields. 

Click on the Calc Opening Adjustment button to recalculate and adjust the Opening Adjustment value. 

Do a test cut to confirm that it is correct and readjust if necessary.