This setting provides two important functions...
Wall Height: This
height used when drawing walls.
Height Between Floors:
This is the default height between floor levels in centimeters if metric,
in inches in US.
This distance is the underside of the lower floor measured
up to the topside of next higher floor. Not to be confused with the in-between
floors you create when you draw floors and drag them up or down manually
with the floor handle.