Because I want to change the way you adress pins...
The origonal headers would be S, as in 13S, 12S, ect...In the normal order... The PWM pins would be the standard ones. And the S stands for Shield.
The new proto headers would be in another order... They would be PWM on 13 - 8. These proto headers would be adressed as P13, P12, ect. P stands for Prototype / Proto-Board.