My meter maximum is 33 mmol/L. I once went over that but it must have been an error because I did it again and it was in the 10s. You'll learn how your meter behaves with experience.
My meter manual says not to be worried about the occasional reading of 11.0 but to talk to the doctor if it is frequently over 11.0. My DN says something along the same lines but uses the figure of 15.0.
With time, as you get to know your foods, you will most likely get it down to the 8s and 9s, then 7s and 8s and so on. Losing weight, taking exercise, eating the right foods and you can bring it right down.
But, you will always get the occasional weird meter reading.