not exactly sure, but here's what i did.
I ran one tank of 20:1 and then went to 32:1 after that tank was gone.
that was in 2009, and that engine is running strong with plenty of power.
I did the same with my second engine, and that was in 2010...still going strong with more than enough power.
there are many opinions on breaking in these engines.
some will say to go with 20:1 and ride it hard right out of the box.
Others will say to go with 20:1 and baby it, varying the throttle and not holding it in one place for too long. keep your riding time to about 30 minutes at a time, and let the motor cool for at least 30 minutes between each ride.
I used the varying the throttle method with 20:1 and i didn't go full throttle until i started running the tank of 32:1.
i'm not saying that this is the correct way, but it's what worked for me.