8m was just an estimate from the organizers by the look of it, and no method or analysis seen, so not very trustworthy
But clearly a very large protest overall. I didn't see hardly any media coverage of it - that's disappointing. What was the media coverage like in the US, on TV etc, what about social media.
Sadly you can get more media coverage with a smaller number of people if you are doing some crazy or very novel or breaking the law