I was disappointed to discover that the count up counter for iTunes quit early. So one can only guess when exactly the 10 billionth download occurred. Watch the 24 second clip to see what happened.
I did my last estimated guess for when the counter would reach its goal just before I went to bed at 2:30am. Since ETA was 5:30am and I wasn't willing to stay up or get up early to watch it live, I sort of TiVoed it using a screen capture video app.
Also, I'll have a detailed description of my effort in predicting this outcome posted soon.