Where the 8,000 came from, was the original poster saying that it was 500 billion years old, with mass extinctions every 62 million, which equaled 130 events. The 8,000 was a sarcastic comment regarding the incorrect maths.
I fully understand the current known facts, and the maths.
I was just curious where the 500 billion number came from that 'MichaelDavidCrawford' was making sarcastic replies to.
Start with this comment to clear up your confusion.
Why 500 billion? Where does that number come from?
That's what started this whole mess...that linked(above) comment. 'wjcofkc' is the one that provided the 500 billion number, 'MichaelDavidCrawford' commented sarcastically about the 8,000 events to point out the math error, and then I joined in trying to find out where 'wjofkc' was getting the 500 billion number from, then you tried correcting me without knowing what started this(my guess).
Nothing more than the natural confusion when entering an ongooing conversation without the context of the 'root' of the conversation. Happens to me all the time! :-)