5×1028 was almost certainly intended to read 5 times 10 to the power 28. ARIN's original announcement can be found via https://news.ycombinator.com/item?id=102

5×1028 was almost certainly intended to read 5 times 10 to the power 28. ARIN's original announcement can be found via https://news.ycombinator.com/item?id=10276711 https://news.ycombinator.com/item?id=10276711, by the way.