There were 4 original tire offerings for the Super A. Since then, size markings on tires have changed. The new size markings don't reflect much difference in the tires themselves, just a difference in how they are measured. During the transition, both sizes were marked on a lot of tires, like "9/9.5-24". They all were on a 24" diameter rim. The sizes, in both the old and new markings are:
8-24 8.3-24
9-24 9.5-24
10-24 11.2-24
11-24 12.4-24
Rim widths were normally 1 inch less than the tire size. That is, the rims for the 4 original sizes were 7, 8, 9, and 10 inches. Under the new markings, the tires were measured at their maximum width. Changing rim widths altered the measurement, thus the additional labeling of the rim width such as "on a 9" rim". The rim width callout was usually more than the size that had been used with the older tires.
By the way, I don't think I ever saw a Super A with 8-24 tires and the offering was dropped after a while. The 100/130/140 all had 9-24 as standard. Later on, the standard for the 140 became 11.2-24. The 140 parts catalog only lists 8 and 9 inch rims.