There's posts dating back all the way to 2008 about this. So it's been around for a long time. I would have to do some serious detective work to find out what version it was introduced. But it's a common question that could be found using search and am surprised that it was unknown. As far as where it is documented, probably the best place would be Default Controls section on GameEx's website. Here is the exact part I'm referring to. Default ControlsDon't exit Attract mode3, 5 or 63, 5 or 6Button 6Credit 1 or Credit 2