Thanks for pointing that out, you are correct. Sometimes when I write these guides its very late at night after a long day at work so sometimes I do stupid diagrams 
. To the flat side/shorted leg of the LED goes to the IR- pin, and the round side/longer leg of the LED goes to the IR+ pin. 
I will update the diagram to avoid anyone soldering it wrong and wondering why the LED;s dont work on raceday 