From SSBA Knowledge Base

Scouted Vs. Real

There are two different potential ratings for a player. Scouted potential and real potential. Scouted potential is what is displayed on the pages, on the rosters page, on the free agents page, on the draft preview page, everywhere. Real potential is not listed anywhere. Real potential does not necessarily correlate to scouted potential, as someone can be scouted as a 'C' potential but really have an F potential, and vice versa.

Potential scales

When someone is listed as a 'B' potential (or any other rating), there is still quite a bit of ambiguity as what that really means. A guy with a 79 is going to improve substantially more than a guy with a 61. Here are the scales:
A: 80-100
B: 60-79
C: 40-59
D: 20-39
F: 0-19

Purchasing Real Potential

Becuase of the uncertainty of the potential rating (imagine a guy with C real potential but B scouted potential, you could be thinking this guy could have a potential in the upper 70's, but in reality his potential is in the low 40's), it is possible to buy potential (as discussed in the Team Bank section of the rules page). When you purchase the potential, you will get the numerical value of the real potential.