Hi DIY,
It's nothing to do with using Mach3 in DEMO mode.
Scorpion.tap was prepared in metric (mm) units and the code contains the appropriate G21 command so it should have a dimension approx. 206mm x 235mm.
Could you please try the Axis Calibration feature (Settings page) and follow the on-screen instructions to check the calibration of your machine.
Tweakie.