According to this comment on Quantum Computing StackExchange,
For a decade, until a 1955 lightning strike, ENIAC may have run more calculations than all mankind had done up to that point
I search from some sources with a quick google search, and found this article, saying more or less the same thing:
Penn professor Irving Brainerd once even speculated that during the 80,223 hours ENIAC operated, it crunched more calculations than had been performed by all humanity since time began.
However, I can't find more details about this, like how they estimated the numbers of calculations made by mankind in history.
Are this affirmations true? Had ENIAC run more calculations than all mankind had done up to that point?