Took a walk on the dark side tonight

[SunSeeker]

6. I imagine they were NYU students, since it was at NYU.

No Sanders supporters are providing links for that 48k figure, and the 27k figure came straight from the BS campaign via a press release.

Like you, the only independent estimate I saw reported was 11,500:

Sanders held a rally in Washington Square Park, which was closed all day Wednesday at the request of the Secret Service. 6,500 people were estimated to be in the park for the rally with an additional 5,000 supporters outside the park for a total of 11,500.

http://abc7ny.com/politics/bernie-sanders-holds-big-rally-in-washington-square-park/1288865/

And of course, the rally was held at NYU, to be closer to BS's base. As is typical at BS rallies, most of the audience was young:

The crowd -- largely comprised of young people -- filled the park and crowded the adjacent streets. Many people -- visible from the windows -- also viewed the rally from apartments and New York University buildings surrounding the park.

http://abcnews.go.com/US/bernie-sanders-kicks-off-star-studded-massive-rally/story?id=38377917

The student population at New York University is 57,245. https://en.m.wikipedia.org/wiki/New_York_University NYU is a huge University. So, I would imagine the bulk of the attendees were NYU students. And considering the size of the student body available to attend this rally, 11,500 was not all that much.