I've noticed that as well ... i eat a few atkins products like their morning start trail mix bars b/c they have a lot of protein and are a healthy snack (at least i think so) .. anyways it has 13 grams of carbs in it and then it has a note under saying 3 net grams since 7 g are from fiber and 6 from glycerine which have minimal impact on blood sugar. i've also heard a lot of people say that you can subtract the grams of fiber from the total carbs since ur body passes fiber ... i think thats the concept behind it.
