If the age of the universe in approximately 13.7 billion years the 20 billion years figure is wrong. If the merger occurred when the universe was at just 40% its current age that works out to about 8.2 billion years ago. Not sure how the author worked the math. And, of course, that is assuming we have pegged the age of the universe correctly at 13.7 billion years...
But Monisha says they have the receipts.
I guess that means they have 30 days to return it for a more accurate one.