The Drive Byes always inflate the left's crowd numbers at their gatherings by 50%, and deflate the Right's crowd numbers by 50%. So the correct estimate should be between 4500-5000. Which, from a trained observer's eye, looks about right.
5.56mm
The news media might say a few hundred. But we know better!
http://www.youtube.com/watch?v=fwyDWHjNJ6c
http://www.youtube.com/watch?v=Xpn1J9Nt4e0
http://www.youtube.com/watch?v=z2H8xHFXC8U