Mr. 99 was born with a Tier 5 magic potential but he had only reached the peak of the fourth tier even after so many years of training. Magic potential didn't necessarily guarantee the level of magic one could use. Just as the term 'potential' suggested, it was just a marker that indicated what level of magic one would be able to use provided they practiced and trained hard enough to reach it
In a way, it was also a limiter that could not be broken. For those that had a high magic potential, it would be a shining beacon that provided hope and gave them the motivation to work harder. A goal that they could achieve as long as they were dedicated to the cause.
