Check your owners manual for the fluid capacity and go by that, or do a Google search and find a number. Unless you get the car level in the air when re-filling (and most people wouldn't when doing this themselves), it'll be a little overfull since the transmission is leaning back and effectively raising the fill hole. It's probably not enough to make much difference but be aware of that.
I'd like to know if the Getrag trans fill hole is at a place that corresponds to full, when I changed trans fluid a while back I don't think the specified 2.1 quarts filled it to the point
of fluid dripping out the hole, but I had the front end in the air creating the situation I described above.