Dear Beverly,
You ask a good question and one that comes up a lot. Package labels must indicate the nutrients “as packaged.” If the unpopped microwave package contains a half-cup of popcorn kernels, oils and flavoring, and if the nutritional analysis is based on a half-cup serving, then the nutritional analysis will read high in its pre-popped form. Of course, nobody eats popcorn kernels raw. Once the popcorn is popped, the volume expands and you might end up with 4 cups of popped popcorn. Again, if the nutritional analysis is based on a half-cup serving you will now have 8 servings per bag. The amount of oil and flavoring remains the same, but you’ve gone from 1 one-half serving pre-popped to 8 one-half servings popped. The oils are now spread out among 8 servings, so the nutritional analysis will read much lower.
I hope that clears up the mystery.