I'm almost certain they meant character size, or rather, how many can a person control. Like can I only have two(Say, Adin and Worren), or can I have an upper amount, like say

Rilla
Joseph
Worren, Trent, Derik, Jet, and Levius
Nihl and Terra
Adinraen
Diketsu
Kimicho
Kei'Taro
etc., etc.