Dahak,
Actually, I found a link the first ten minutes of the video of the announcement, so you can hear the exact quote yourself:
http://www.youtube.com/watch?v=dPRJArsQjxk
"Where we have Kindle editions, Kindle sales are now 35% of books." According to the chart it went from 13% in February to 35% in May with the launch of the Kindle 2. During the Kindle 1 period it was in the 5% - 10% range.