We walked up around 9:15 to look, we were on our way to Test Track. No one in line and nothing going on. We returned after our ride at 9:45 and there were about 4-5 parties in line. We joined the line. Folks in front had done before and said they come out at 10:30 to start offering reservation times. By 10:30 there were about 20+ people in line (I know a couple were holding the line for their whole group). The first party was looking for 7 people, one in front of us wanted the bar. They slowly went through and the bar people stayed behind.
Times offered were based on your party size and what they had opening. The couple in front of us was offered opening at 11:30. The party of 7 was given afternoon some time. Our party of 3 was offered 2 pm. Had they offered dinner we would have passed on that price point.
Our day at opening there was one line. There is no one out there to even organize two lines so everyone got in one. As folks got their restaurant times it left behind the bar people. I assume as time went on there might have been two lines developing though. When we went back to eat there was only the bar line, I assume it doesn't take long for open reservations to be filled.