When you create an override for a dimension value—entering a different value, hiding a text or a segment, adding a prefix/suffix—the override is marked by a small overline above the changed value. The overline is useful for seeing at a glance which values have been overridden.It is also useful when you have hidden texts and segments, to select the hidden segment.
In some cases, however, you might want to hide the overline. The overline is placed on the DEFPOINTS layer, and by default is not plotted.