There is no technical limitation on how many people can fit into one Knit Space.
If you're planning a large event, however, you might want to think of having several thematic Spaces and thus split up the participants. Keeping Spaces cozy can enable deeper interactions amongst guests.
For example, for a recent careers conference, we've seen three thematic Spaces, for consulting, tech, and social job seekers. Each lounge had its own cool name: "Big Four", "Silicon Vinery", and "The Bar".