The Wall Rangehood (RH) cabinet has the ability to undersize the cutout depth of the undermount cutout (when the rangehood type is set to 'Undermount').

This can be done on the Labour & Construction > Hood page, in the Cutout group box:

Reduce Machining Depth of Undermount Cutout

Reduce Machining Depth By

The amount to undersize the undermount cutout. E.g. setting this to 1mm would take 1mm off the machining depth of the cutout.

Current Cutout Depth

Displays the current machining depth of the undermount cutout.