What time do NJ Transit 308 buses leave Six Flags Great Adventure for New York City?

I'm planning to go to Six Flags Great Adventure on NJ Transit bus 308 from New York City on Wednesday 22nd June (2011). I've found information on pricing and departure time of buses, but can't find any information regarding return time from the park. The timetable states that buses leave Penn Station at 9.30am, and arrive at the park about 11.20am, but I can't find any information on when the buses back to New York City from the park are. Can anyone help?