I think that's exactly the point of the article: people have no good way of knowing how many people show up, especially if they "were there" ... This is the first time that someone has done something systematic. It may very well be that:
> that was the biggest I have ever seen
... but until you find a way to sell tickets or something, just saying "well this was WAY BIGGER than the one we don't know about but someone thought was 100,000" is just a perpetuation of the problem.
That is, if you believe that these numbers "mean" something.
(I don't)