Regarding alexa rank on website

Hi,
Just want to know about alexa how they are giving rank to websites. Some 15 days back my friend told me alexa has been removed India base ranking from his site. After that he contacted with them and alexa representative told him that he does not enough visitors from India. But he has checked Google analytic and found it he had visitors from India almost 2000 visitors.
Just worried about this… So kindly guide me regarding how alexa is giving rank?
Thanks

See original post by linkkingseo