"Okay!" Would Two like to pick a direction or should Bruce do it? It would be very on theme for this place to be shaped like the inside of a torus such that it doesn't super matter which way they go.

Two sets off in a direction!

The Zeroes get distracted playing with a board game they found. 

They pass sports equipment, books, trees, a karaoke machine...

The only way that's different from normal dreams is that they're not in his middle school building . . . oh hey, books, if he snags one off the ground can he read the text at all?

He sure can!

It's a picture book about numberblocks in which One wants to paint, but Four wants to climb trees. They argue with each other, but eventually decide to take turns playing and climbing trees. 

Oh sweet, he's literate! He's never had a dream (lucid or otherwise) where text worked right before and it has always sucked. Also: adorable number children are adorable.

"We get a storytime before we go to sleep."

"That's a good thing to have. Reading is important. Have you learned to read?" He sounds like a PBS show but it's not like he has any better scripts available.

"Numberblocks don't learn how to read. They already know how to read when they're created. Do Bruces have to learn how to read?"

"That's neat! I didn't start out knowing how to read but I learned a long time ago."

"How did you learn?"

"I don't remember all the details, but other people showed me all the letters and told me what sounds they made and helped me practice."

"Were they Bruces too?"

"You know how you and One and Three are all numberblocks? I'm a human and the people who taught me to read are also humans but they aren't Bruces. There isn't a magic mirror where I'm from, and people can't split or combine, so I'm the only Bruce there is."

"That's so weird!!!!!"

"Yeah, it's pretty weird." Just wait until you hear about the process for creating new humans. It's going to be a long wait because no way in heck is Bruce explaining it if he can get away with not that. "Where did your mirror come from?"

"When One appeared, every kind of thing that existed already existed. But only one of them."

Seems as plausible as anything else but also like a really cool creation myth. "Huh. And there couldn't be two of anything until some Ones combined to make you the first time?"

"Yes, because I can duplicate things! See?"

Now that one tree is two trees.

"That's so cool! . . . Can you duplicate me?" And this is why he shouldn't be trusted with anything important eh, whatever, it's a dream, worst he can do is annoy himself.

"I'll try!"

Bruce is noticeably unduplicated.

Safe from the consequences of his choices for now, eh? "Hm, looks like a nope. I'm pretty odd, though. Well, pretty weird, at any rate; my cardinality modulo two is anybody's guess."

"I have no idea what any of that means!"

"You know how you can split into two smaller numberblocks that are both the same size as each other? That means you're even. You know how Three can't do that? That means Three is odd."

Look, it just doesn't seem right that his subconscious mind's abstract personification of the number Two might not know all the math he does. And all the English words for discussing that math.