But here it's not about a generic lack of realism (there's plenty of details you could point to, but it would be of course silly) but simply the internal contradiction in what the main character says: claims that the station is "as big as the cosmos" and two lines later provides an estimate for its diameter that is grossly inconsistent with that same assessment. Unless they live in a universe that is only 15k years old, which is also possible (but clearly not serving a purpose in the story).