Streams of numbers make me a little nervous. Both the lizardmen and the Numbers World is perplexing. They both actually remind me of numbers stations. Look it up on Wiki, it's rather disconcerting.
I think the whole random number thing is sort of based on three things.
1) The first is a common phenomenon in lucid dreams. When you look at clocks or words or whatever and look back at them later, they rarely appear the same way. On a Famicom, the main transmission of information is through text. It would be rare for that text to not be nonsense and (pseudo)random numbers are a way of portraying that. In Numbers World, these numbers don't change but they're so scattered and so large that they might as well be random.
2) The second is psychological and explains way more than just numbers. Mado might suffer from recurring OCD (and maybe pareidolia). This could tie in with the hikikomori theory in some way; she's just too paranoid to leave her house. Her mind might be seeking order or trying to seek order.
She is constantly haunted by the disarray of Graffiti World, vague images dissolving into nothing. She may be futilely trying to construct order and architecture in the Cube World, constructing intricate but meaningless patterns in the Darkness World.
These disorders isolate people, causing anxieties about those who might disrupt the daily rituals in her life. Mado may even be enslaved by these compulsive rituals, manifesting abstractly as the Aztec spiritual imagery common in the game. The dream world, in this case, is an absolute nightmare and frustration at a growing paranoia and desire for order.
The disordered numbers may reflect this kind of nightmare.
3) Kikiyama is just being weird.