PS2 Connection to Arduino

I'm trying to connect a Sony PS2 Shockwave to my Sunfounder Mega 2560. I have looked at http://forum.arduino.cc/index.php?topic=102901.0 to try and understand the PS2 pin to Arduino connection but I'm stumped. I see the pins labled 1 through 9 for the PS2 and I expected to see a corresponding list of arduino inputs such as 13 or A2 etc. Any help would be great.

I've just quickly looked at the link: There is a picture with coloured leads, annotated with their (assumed) function. There is also a line of code which maps Arduino pin numbers to these assumed functions with comments:

ps2x.config_gamepad(3,5,6,4, false, false);   //setup pins and settings:  GamePad(clock, command, attention, data, Pressures?, Rumble?) check for error

So, for example, the blue clock wire is connected to pin 3 on the Arduino, or at least, that is how I interpret it.