In any session, you and your presenters are able to share up to 64 different microphones and/or webcams at the same time. This is default behavior across all sessions.
If you are still using the classic dashboard, you can access this setting in the Webinar Dashboard under Manage Webinar. Scroll down to Webcam Experience and choose your setting. 9 camera mode is a legacy setting, and should not be used outside of specific circumstances.
Note : Once you hit 64 individuals on camera no one else will be allowed to share until someone turns theirs off or a presenter disables one.