He and Treyton weren't putting a lot of things in their space for the time being because they were filling up Theo's space.
They couldn't use their space in public anyway, so they had to put more things in Theo's space first.
So, of course, Theo's space needed to have more of the things he wanted so that he could always ask him for them if he wanted to have them.
"Theo always remembers that your space is your own ability, so you can always put more things you want into your space.
For example, putting more of your favorite food, clothes, toys, and other things. If it isn't for you, it can also be for Sophie, Jane, or other people that you like.
Treyton and the others only taught you to always leave half for other people that will come in later.
So, you can always add more things that you want in your space as long as you still remember to leave something behind.