2000 Chrysler Sebring Transmission Fluid Fill

I brought my Sebring convertible to a mechanic who checks the transmission fluid while the engine is running. He said it needed fluid but over the next 4 months it kept leaking tranny fluid all over the driveway. Then it stopped. I ran the engine till hot, shut it off then checked the fluid and it was right on the full line on the stick. Not sure if this is the proper way to check and the manual doesn't give instruction other than to say the engine needs to have been running for ~20 mins.