62-65 early model speedometer gear Chart?

With apologies to the OP for a minor hijack along these same lines.

Has anyone used one of these to calculate gear tooth count?

It comes up to 41 tooth... Which based upon the follow-on charts is accurate as I've used navigation apps to track speed and compare to tach.

Seems off to me. What am I missing?

RPM and Tire size ratio calculation.jpg