If the diamond shape is on the back side, change the back side.
If the diamond shape is on the front side, change the front side.
The top-right corner and the bottom-left corner. a in the figure above.
For example, the distance is 336.0 mm (13.23").
The top-left corner and the bottom-right corner. b in the figure above.
For example, the distance is 335.0 mm (13.19").
In the example, the measured difference is -1.0 mm (-0.04").
If the media registration is not optimal, change the value or use another setting depending on how the registration looks.