The 3D clearing strategies (Adaptive Clearing and Pocket Clearing) as well as the Contour finishing strategy have a setting on the Passes tab called Flat area detection. When enabled, the strategy detects all the flat areas and adjusts the stepdowns to ensure that the axial stock to leave is left on these flat areas.
The Flat area detection setting on the Passes tab
In the image below, the stepdown is set to 1 mm and with a stock to leave of 0.3 mm. Since the stepdowns do not follow the heights of the flat areas, the actual amount of stock left on the flat areas will be more than the requested stock to leave.
Flat area detection disabled
With Flat area detection enabled, each stepdown is adjusted to match the flat areas such that the requested axial stock to leave is also the stock left in these areas.
Flat area detection enabled