Although there are no specific quotas for schools to meet, as that is illegal, schools are able to consider applicants and their race on a case by case basis, and give preferences to certain groups in order to maintain a diverse student body.
This means that for an over-represented minority group such as the Asian-American population, the school will be inclined to accept only the best of the applicants in order to limit the number of Asians accepted.
As a direct result of this, a stereotypical white American may be accepted for a 3.6 and a 30, because there are so many more Asians with similar numbers applying, the Asian kids accepted will likely have higher stats, representing the cream of the crop.
The opposite is true for African Americans. They get a slight break as a result of schools wanting more African Americans in order to achieve a diverse student body.