Doesn't these calculations assume a) 100% load factor which while desirable is not always possible, and if not achieved pushes the average ppp downwards and b) no cancellations due to low viz, ash cloud, blocked runway etc, which pushes the movements downwards and thus the average ppp up assuming rebooking. Suspect that they don't cancel each other out, and average yield (BA is something like 80% I think) wins....
Factor that in and you are looking the need for more movements to fill these terminals.