I've created two circles, one larger (16mm and 7 mm) within another (they are T nuts for a waste board). I selected and created a tool 6mm end bit. I selected the Gcodetools extension for orientation and saved the file as DFX R12. 

I load it into Lazycam then separate one circle into a new layer. I give layer 1 a layer depth of 22mm and layer 2 the larger circle 2mm for the T nuts.

When I load the job and cut this the bigger outer circle always comes out 10mm diameter when its supposed to be 16mm. No matter what I cannot get the second circle to 16mm diameter. What am I doing wrong? 

Im using a scap of plywood to experiment