Methodology? (Score 1)

Regarding the statement:

During the first 29 days of October, 1.2 million people worldwide visited the 'In Rainbows' site, with a significant percentage of visitors ultimately downloading the album.

I was wondering how they arrived at the "1.2 million people wordlwide" figure. At first I read the "About" Statement at the bottom of the page (http://www.comscore.com/press/release.asp?press=1883) which reads

This capability is based on a massive, global cross-section of more than 2 million consumers who have given comScore permission to confidentially capture their browsing and transaction behavior, including online and offline purchasing.

After reading this, I intuitively assumed that the 1.2 million was the proportion of the "2 million consumers" that were being voluntarily BigBrothered by comScore who had visited the site, but the press release sounds as if they are referring to the actual sum of ALL the visitors to In Rainbows dot com (plus, that would be over half the entire network of comScore participants - a HUGE number). The methodology page here http://www.comscore.com/method/method.asp mentions that they use a "statistical methodology to enhance the accuracy and reliability of projections to the total population based on its network." but does not go into much further detail regarding the actual process. I was wondering if these numbers are reliable and if anyone could shed some light into the actual methods used to gain these numbers.