The dxf is no good that you posted. Base on the posted code, the pathing of the file is as shown.So if you cut on the line with a .25" dia cutter
the outside diameter should measure 6". Note that the start point is very far away from drawing 0,0,0,.
You can calculate the steps per unit for each axis or use the axis calibration feature of Mach.
You may want to calibrate based on the longest axis move possible thus inaccuracy wil be less at shorter distances.
Seeming to move without measuring is of no value in CNC work.
RICH