Also, i believe they get the factory numbers by testing the engine at the crank. The dyno's we all use tests the bike at the rear wheel, so there is always power loss from the chain and transmission etc. Also like Playful said, bikes with ram air cant suck in air while they are sitting on the dyno, so you dont get the complete HP reading.

So you take the power put down on the rear wheel and add i dunno 5-7 horsepower for the ram air and you should get a ballpark of the amount of total power put to the pavement.