Accuracy to an integer would be 31. Saying it is 30 is a pretty large error for one whose eye is on the sparrow and can count the number of hairs on your head.
There's a difference between error and imprecision. To be more precise in your language you should have said. "Saying it is 30 is pretty imprecise for one whose eye is on the sparrow and can count the number of hairs on head."
If God is too imprecise for you here, I think that is between you and God. As for me, the very fact that God choose not to be more precise here is telling me that in this particular case, preciseness beyond the approximation is not needed.