The 4S had 1m preorders and opening weekend sales of 4m. With 2m preorders, it's easy to assume they had doubled capacity so 8m or more. When you are guessing and dreaming, you can pick whatever numbers you like.
Apple's best quarter this year was 37m iPhones so 410k/day.
The event was on the 12th, it is now the 24th so with the same capacity that gives them 4.9m in 12 days.
If this is the case, it'll be 7-8m in the 1st week. If they manage over 9m in the 1st week then they will be on track for the 50m unit quarter (total iPhones).