This can vary a lot! As soon as you stop the engine, the converter begins slowly draining back into the pan. If the pan is off for a long while (several hours or more), more fluid is lost than if the pan is put right back on. If the pan is removed after the car has sat overnight, more fluid is lost than if it's removed right away. Hot fluid will drain back faster than cold fluid. So there's no clear-cut answer. That's why there's a dipstick and the book says to make a final check with the engine running and the trans warmed up. If you have a whiz-bang chrome dipstick tube, put in a stock tube and 'stick to get the right level then reinstall and mark the chrome one.