The numbers are from a blog in the BW forums. The original source is the Stanford website for recruiters. As I mentioned above, it is unconfirmed but I believe the source is legitimate.
Now, regarding the your comment that there might be 50 super-elite Indian candidates (or Chinese candidates) - no doubt I totally agree with you. That's why I have pointed out time and again that people in these over-represented groups who believe that they have legitimate shots of admission with 650 or 690 or even 710 GMAT scores are just dreaming. There are dozens and dozens of applicants with 760+ scores with interchangeable background and it will be more or less to distinguish yourself simply through "writting better essays" or whatever. The average GMAT at Stanford is 720, and the average GMAT for those from these highly competitive demographics is probably 750+ ... yes that's right, the average.
I have also pointed out elsewhere that quotas are against the law in the US. Calling up a school and asking whether they use a quota is a waste of time. The Bakke supreme court decision specifically states that quotas are illegal. However, the same decision says that race may be used as a factor in admissions. Highly divisive decision that has been around for a lot of years. If the sujbect interests you, you can find 50 books about it.
Regarding the comment that they are racist? No. I honestly believe their stated policy that they want diversity. When you say there might be 50 qualified candidates, that's not really true. They want a class that reflects different views and opinions, and having 50 Indian/IT/Engineers has aboslutely no appeal to them. They want a diverse class so, regardless of what adcoms tell you to your face, you are in fact competing with the others that have the same demographics as you. If they happen to have higher GPA & GMAT, better undergraduate school, better work experience and better extracurriculars, then it's going to be d@amn near impossible to beat them. It's nothing to whine about, it's just the way it is. Chinese and Korean undergrad hopefuls have been fighting the same uphill battle at places like Harvard, Stanford and Berkeley for years. Average GPAs and SAT scores for Chinese and Korean undergrad applicants obbliterate all other demographics, including the rich white folks, yet they are admitted in much smaller numbers.
About 8-10 years ago (as I recall off the top of my head) race was removed as a factor in UC admissions (including Berkeley and UCLA). The demographics changed from about 30% asian to well over 50% asian, even though the applicant pool was only about 20% asian. It only lasted a year and they quickly adjusted their policy, but by merit and scores along, tons and tons of asians are turned away from the best colleges each year so other may be admitted.
Necromonger and ap663 are exactly right. Becuase they want a diverse class you must distinguish yourself from those with the same basic demographic. The simple fact is that there are just loads of people with the exact same Indian/It/Engineering/Male background and, just remembering that these are business schools (not engineering or CS) should make it clear that they will not skew their student body with a single group.
I did also note, while browsing the Stanford recruiting website that 52% of the Class of '06 and 47% of the Class of '07 had Humanities/Social Sciences backgrounds. That makes me pretty excited with my English & law degrees.
Anyhow, the numbers weren't meant to inflame anyone. I hate it when people rant and rave about statistics. There's no use arguing about them, that's just the way they are. As mlohani and Hindustan pointed out, they serve mainly to put things into perspective. Of course, Stanford is probably the most selective of all the schools, so things will be different at other places. But you can look at the statistics at any school and assume that there is an extremely high correlation between lower than average GMAT scores and with diversity admits. A very large potion of those admitted with below average GMAT scores are admitted because of diversity factors. At many business schools, being a woman is such a factor (a duke adcom said it was a very favorable factor). On the flip side of the coin, nearly all of those from over-represented demographics must score higher than the average GMAT. That's just the way it is.