That's the dollar estimate in the first 24 hours in the US and Europe. That's compared to 170 million for Halo 3 when it was released in 2007.
As is the tradition with these things, Microsoft made the obligatory comparisons to Hollywood movies, sizing up the initial “Halo: Reach” sales against the three-day opening weekends of "Iron Man 2," "Alice in Wonderland" and "Toy Story 3," and declaring the video game “the biggest entertainment launch of 2010 in the U.S.”
Of course a movie ticket is ten bucks and Halo Reach costs 60. Still, that's a lot of people willing to shell out 60 bucks for a game.
By the way, this is my new favorite video ever: