He's starting to lose Cal again. Cal can deal with the idea of a world inside computers as long as he doesn't think too carefully about the logistics or where things go. But once he starts trying to apply concepts like cities, he gets lost.

(Cal is aware that it's not quite the same as a physical planet, but that distinction becomes difficult to hold in mind when talking to a boy who exists physically and is not just abstract programming.)

He still nods like he totally gets it. "What would be an ideal number of Guardians?"