Is there more fibre in the paper box or a serving of corn flakes?

The box. The box could probably count as fiber, since it is undigestable plant material. However, it isn't a food item per-se. Anyway, there are many cereals with more fiber than corn flakes. The older i get, the more tempting that box gets.
Yes. You mean the fiber in the box that hold corn flakes than the fiber in the corn flakes, then weight per weight yes . Edible boxes are not made yet !