With you there...the scale marker should be the screen. You wouldn't expect to read a number on a map, and then hunt for the small print to tell you that the number refers to the size of the whole map... (ok stretched analogy, but still valid...)

We don't actually need the serifs though. If you look at most maps, the scale marker is usually drawn as a line of alterating white/black sections, where the length of each section is a known quantity, and usually correlates to grid size... eg on British 1:50000 OS maps, the section is 1km in length.. (Actually, IIRC they have an imperial scale as well, but you get the gist).

We could do a similar thing with the current dividing line - with VFDSHADE_BRIGHT and VFDSHADE_MEDIUM sections, and get the benefits of a real scale, without using any screen real-estate