Effective only during Z-level rough, a non-zero Toolpath corner % enables raceline smoothing by replacing sharp corners with rounded corners. Defines the maximum deviation from the sharp corner. The maximum this can be set to is 40% of stepover. This means that if you have a 10 mm stepover the maximum deviation from the sharp to the rounded corner is 4mm.
Using the Toolpath corner % produces a toolpath with fewer small arcs which makes the toolpath more suitable for high speed machining. The original profile has the same number of points, but the offset passes have a reduced number of points.