The A1 or B2 or whatever you have the screen set on stays on the screen when you press the + key, but it actually defaults to just A+, B+, or C+. Don't get caught up into thinking you can have A1+ or A3+. Your options are A1, A2, A3,or A+ then likewise with B and C.
I've seen senior drivers at Nationals and Regionals the don't even know how to put in the wait time.