Sill Height Using Subfloor Thickness

ARCHICAD will still measure the sill value from the wall base, but the door/window marker will show a sill height value that subtracts the subfloor thickness from the entered sill value.
Note: Entering a value into the Subfloor Thickness field does not affect the actual positioning of the door/window within the wall; it is merely an alternate way to display sill/header height in the door/window marker.
Note: Sill height markers use dimension units set specifically for this type of value: go to Options > Project Preferences > Dimensions, and choose Sill Height Dimension.
Some markers have a checkbox to display the Nominal Sill Height (e.g., the displayed Sill value does not take subfloor thickness into account). The illustration below shows the effects of unchecking and checking this box.