You will be fine breaking it in with 15%, just run it a bit rich so it stays cool.

Looks like an oversight by the manual writers. Set the needle valve for break-in, and the do the break-in procedure. After that you may want to reset it for flying, but you should be good after breaking it. Like the manual says, lean it out a little bit for each flight after break-in. I have a good rule of thumb I use when flying, tune it to peak RPM and then turn it back 2-4 clicks to the rich. I like to see a bit of smoke in the exhaust when I'm flying. If you run it rich like that the motor will last for a long long time

Ken