When you see something so orgasmic (like walking into a bar and seeing your entire league of kickball teams playing flip cup on 8 different tables, or Bar Rafaeli naked) that you feel as excited as you do when you get hard. Thus, you go from the 6 position (on a clock) to the 12 in your head, hence going from 6 to 12, or just 612. Other uses: 612 mafia - for all those in the know.
Dude, when I saw the Red Sox hit 4 straight homers that one year, yea, 612. But last night when I was too drunk to get it up, I couldn't even get to 630. Good thing too, she was ghastly.