Again, accurate. You'd need 100 events as large or larger than St Louis, at a minimum, to approach two million participants. Didn't happen. There were more like 10 or 20 that size nationwide. That makes 200,000 a reasonable number. One look at the 100 largest cities in the US shows that you can't get there with the known turnout determined by measurement.
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So, as always, the organizers have grossly overstated--and it's reasonable to expect them too--the turnout for their event.