Women say they quit Google because of racial discrimination: 'I was invisible'

> “He said, ‘It must’ve been really easy for you to get your job because you’re an Asian woman and people assume you’re good at math,’” Zhang recalled in a recent interview. “It was absolutely stunning. I remember me just emotionally shutting down.”

Can someone explain what is stunning here? Is it some kind of sexism or nationalizm? Or maybe she had a lot of troubles while applying to job because of her sex and ethnicity, and that white male colleague devalued it by stating something that strictly reverse to reality?

I myself like to belong to group presumed to be good at something. It is very convenient most of the time. It could bring some inconveniences if I'm worse than average in that group: its embarassing to explain that I'm not so good as people presume. But if I'm good enough, than there are no problem at all. But I'm white male and, by definition, cannot understand asian woman.

I eager to learn what is wrong with that, will be grateful if someone explain it.