As far as I know, it's just a reader convenience survey.
As an example, taking a sample one from November 12th (gonintendo regularly posts them): The top is still the same as today (FF13, BH5, MGS4). Blue Dragon is #3, Twilight Princess is #6. So far, Wii Sports and Wii Play have each sold over TWICE as much as Twilight Princess in Japan, yet didn't even make the top 20 list. Blue Dragon sold even less, only 140,000 copies so far.
To sum, two games that sold over a million copies so far didn't make the list two weeks before release and the #6 game has sold 3 times the amount of #3.
It only shows what Famitsu readers want and doesn't say much about what Japanese sales will be.
9
As an example, taking a sample one from November 12th (gonintendo regularly posts them):
The top is still the same as today (FF13, BH5, MGS4). Blue Dragon is #3, Twilight Princess is #6.
So far, Wii Sports and Wii Play have each sold over TWICE as much as Twilight Princess in Japan, yet didn't even make the top 20 list. Blue Dragon sold even less, only 140,000 copies so far.
To sum, two games that sold over a million copies so far didn't make the list two weeks before release and the #6 game has sold 3 times the amount of #3.
It only shows what Famitsu readers want and doesn't say much about what Japanese sales will be.