That was from the company "Annual Report", which is one of those things that had better be pretty accurate (or you get lawsuits for misleading the investors.) It can still be misleading, though. (For instance, I notice that it doesn't break down the multiple types of microcontrollers that Atmel sells, so it's presumably everything from 8051s to AVRs to AVR32s to ARMs.)
The point is that you don't sell a billion dollars worth of chips in a year to hobbyists...