A groove is made narrower

[denprog]

I want to make groove with the Parallel path. But it always is narrower after CNC than it is in Blender. I tried different options. For example, this picture shows a groove and such path settings: Strategy: Parallel Distance between toolpaths: 2 mm Distance along toolpaths: 0.2 mm Use layers: 5 mm Operation depth start: -1 mm Movement type: Meander / Zig Zag Cutter: End Cutter diameter: 3 mm. The picture shows that paths are too far from the walls of the groove. What's wrong in my path? How to make a groove exactly as in Blender?