It seem that all the workouts, activities, and classes have a count ceiling of 99. This is probably because the UI allows for only 2 digits. I have encountered this on both the run the world all races and the ABS 100% E workout since I tend to do these everyday. I will no doubt run into the ceiling on others but since I mix up the rest of my workouts from day to day it will take longer. I expect that the miles count the the races will top off at 999 since there seems to be only enough room for 3 digits there. I won't run into that for a while since I'm only at 394 miles at the moment. I also wonder if the trophy count will eventually reach a ceiling of 99.
Since this game appears to be something that one would use for a couple of years at least until a newer version comes out, these ceiling limitations don't really encourage sticking with the workout program in the long run.