There is overfill, and the amount is written on the box or in the pamphlet. I don't have my box on hand, but I can check later for you. The amount left after the last dose is equivalent to the last marker on the pen, on some of the pens it is 75 iu. You should only inject your dose amount and not the dose plus overfill. If I were you, I would check in with my nurse or doctor. All of these meds can get confusing!