No no no! Jackets aren't more! There's another thread from earlier today, but the long & short of it is that you need to weigh them raw.
If you boil a 200g (4pp) potato, it'll still be close on 200g when cooked, whereas if you bake a 200g potato, the water will evaporate, and when cooked it becomes a 100g(ish) potato, the amount of potato in there is still the same but much less water, so is still 4pps. Does that make sense? Xx