The rib side defines the direction in which the thickness applies. The rib side does not affect the depth measurement. The first figure shows a rib where the thickness applies within the plane of the profile, and the side was defined as symmetrical about the profile.
The next figure shows a rib where the thickness applies perpendicular to the plane of the profile, and the side was defined as symmetrical about the profile.
Note:
By default, all ribs are offset symmetrically. If you do not want the rib offset symmetrically, click the Side Step button, and define the side of the profile you want to offset.