I ate an Atkins Advantage bar as part of my calorie controlled diet - and very delicious it was too. But I am a bit confused about exactly what to record as the calorie count for it. It has 19g carb, but tells you to only count it as 2.1g. Does that mean the other 17g are indigestible? (ie they show up when you burn the food in the lab, but not in the human body) If so, should I subtract 17x4 calories from the total shown on the pack?