The label gives the height of a wall. It will typically be used for knee walls. It can be used in section or in plan. It will only work as an associated label; select the wall and check the "Label Elements" box.
The value displayed is the height of the wall in the settings. This means that for trimmed walls, you have to "Set wall height to highest point" when trimming, or manually set the wall height to an appropriate value. Tip: trim the wall using "highest point", then round the height UP to the next 1/4", 1/2", or whole inch.
See Also: Labels