That's only true if you test all 311 mio for both. While I think that blindness is self-analyzing, that's not true for schizophrenia.

So how many blind people were evaluated for schizophrenia?

This might actually be a lower percentage than for normal-seeing persons. People are less experienced with the behavior of blind people, so it's harder for surrounding people (and probable even for the blind themselves) to recognize it and push people to go get diagnosed.