The author types at 120 wpm, so that's probably what he recommends. He doesn't say how much work it took him to get there from 60, but it was a conscious decision and special effort. On later occasion, he learned numbers.

Although he clearly advocates such speed, he doesn't really argue for it. What motivated him to speed up was text chat. What struck me as a good argument is that lots of people say that they are limited by what they have to say, not typing speed, but being able to type more gives the option of writing different things, such as more back-and-forth on message boards. If that's actually useful. But I didn't take his advice and still only type at 60wpm.