why would the transmission fluid show overfull only after 3quarts after serv.

What is your question?

after servicing a transmission for a 98 Hyundai Elantra I put 3 qt.of transmisson fluid and it showed overfilled. the car requires 4.5 qts and I changed the fluid twice in a week because the fluid smelled bad the car runs good but its to overfilled. Is there a certin way to check the fluid?