Given the dire situation, I'd hope to see thousands in each protest.
Given the reality, for this to work, it really needed to be presented as a recurring protest if they want to at least have something on short notice with chance for it to grow in subsequent events. Hopefully by the 3rd or 4th protest it actually seems compelling.
As it stands, it seems exceedingly underwhelming. To those that followed nuance, they know that someone sprung this idea on the internet and this is the result of less than a week and a half of planning and the modest attendance is unsurprising. To those that just see what the protests looked like without context, it doesn't seem particularly engaging. When those same people that saw the underwhelming attendance also see people saying that the news didn't make this out to be the biggest thing ever was just because the news is suppressing dissent, they are disinclined to take it seriously.