Plotter measure problem

[tintswe]

Hello!

I have bought one china plotter and it's cut great window tint but i have one problem with the measure.

But the problem with the plotter is that the measure i choose from Computercut example if i  one rectangle piece the measure does not match when i measure piece on the table.

Example i choose cut one rectangle piece 38,8 cm X 38,8 cm and the piece can cut in 39-40 cm.

What can the problem be like? Is there any setting inside Computercut?

I do not think the problem is pinch rolls when the machine does not cut the "whole" rectangle then.