The reason for the maximum of 99 may be that the pedal autocalibrates itself, using the maximum value it sees as 100, and the minimum as 0.
If you hit the pedal hard it may go to a slightly higher value than if you hit it gently. This higher value will be called "100", while the slightly lower value may be called "99."
The difference between 99 and 100 will not usually be audible.
