Did you check it several times. I know that After adding fluid a lot of times fluid stays in the tube and even after checking 5 or 6 times it will apear to look full on the stick but after checking more the filler tube will clear out and you will get a different reading. Also just to make sure. You are checking the fluid with the vehicle running and in park right?
So there is no D with a circle around it on the selecter. Are you saying the fluid was black now when you fist checked it and it was low or when you took it for the fluid change. Im assuming you meant before the fluid change.