One thing that surprised me is that I couldn't find any well-known name for what the * and / operators are doing; digging around on the net and in some dusty old math textbooks didn't yield any exact matches. I ended up adding footnotes with the actual computations, but I'm not very happy with that approach. Surely Lockhart[1] got this definition from someplace, though, and didn't invent it out of thin air.
I'd move the footnote indicator to:
Available for point[a], box, path, circle.
Available for point[b], box, path, circle.
As the footnote only applies to that specific left operand type.
Or maybe:
Available for box, path, and circle. It is also defined for point [a] but it has no related physical meaning.