More info from Jack:
Yesterday Jack rode on the suspicious 300 m cal course. Then he cycled to another 300 m cal course, then cycled to a nearby 1/2 mile cal course. He used a protege electronic counter, so his Jones Counter was not a factor.
He obtained three riding constants:
Suspicious cal course: 480.64 revs/km
Nearby 300 m cal course: 479.03 revs/km
1/2 mile EDM cal course: 478.89 revs/km
This tells me that the suspicious cal course deserves its name. It appears to be about 301.1 meters in length.
Jack is going to do some taping, and to try to figure out how the measurement could have got so awful.