I think the note will always display as a decimal the way you described, but there could be a workaround. Maybe someone else has a better way, but here’s my thoughts.
One thing to try would be to have two separate equations in the graph component, such as N=4 and D=3? Then in the note, try:
content: "Drag the green point to identify the number \frac${graph1.number(“N”)}${graph1.number(“D”)}. Then, click the button see how close you are!"`
I can’t get that to format properly, so here’s the example: