Laser cuts oversize by 0.5 %

We have new ZING Z6040 laser cutter with a DSP type controller, Dell Vostro i5 Win 10 Enterprise running Lightburn 1.6.00.
If I specify a cut length of (eg) 297 mm, the workpiece measures 298.5 mm
ditto specified length 210, actual cut is 211
Is there a scaling factor ?

You may need to calibrate your motor step settings. Under EditMachine Settings, LightBurn has a built-in Calibrate Axis tool to help with that.