I don't know the specifics of the Course 2 seminar, but I've been to several GSU seminars in the past. The classes usually run from about 8:00 am to 4:30 or 5:00 pm.
The seminars generally do not end early on the last day. However, there are usually a lot of people who need to leave early to catch a flight, so the instructors usually try to finish up all of the really important material before lunch time on the last day. The afternoon session on the last day tends to be pretty informal--usually, the instructor will give the students a chance to ask questions. People just get up and leave when it's time for them to go to the airport, so by the end of the afternoon, there usually aren't very many students left. I doubt that you'll miss too much if you have to leave early on the last day.
Hope you enjoy your trip to Atlanta!