There are large errors in auto-measure results in XCS. Generally, the error value is less than 1mm when the thickness of basswood is 3mm in laser flag mode.
#1 Check the Material and the Baseplate
Make sure the surface of the processing material is even.
Make sure the baseplate is placed on an even ground.
#2 Check Material Transparency
If you measure transparent or mirrored material, an error is more likely to occur.
In laser flat mode, measure the thickness of the processing material with a dial caliper or put a piece of white paper above the processing material.
In laser cylindrical mode or open plane mode, you can choose to focus the laser module manually.
Tutorial for manual focusing.