Usually just before the market opens, so around 9:00am EDT.
I'm guessing it's 10 million even. Remember, not all the pre-sales will count as "sales," particularly the 6 Plus models that might not even ship for another 1-3 weeks. And it wasn't on sale in China at the launch date. But even if it is a "disappointment" remember that the more important numbers are next quarter, and this is looking to be big. There is a lot of pent up demand for larger iPhones.