Tried to set unit's per mark to less than one (for a demo project using cuisenaire rods and fractions). When I did this the marks disappeared. See below.
It would be nice if could have legend markers in fraction form as shown below:
That said it's late in the release and as shown above I did figure out a way to create this, so I would say the priority is low.
Also, (I think Richo may have pointed this out before) when I rotate the number line (say 45 degrees) the <x on graph> values are not right. This also I don't see as a big problem, just noting these things here in my e-memory.