Obviously lots of reused cells - multistory titles, seamless branching etc. (titles 4, 8, 9 and 10 contain substantially the same content - maybe exactly the same but different command structure). This is entirely legal within the DVD structure.
You can construct this yourself if you like - take any rip and open it in PgcEdit. Just run the make a new play all title function a few times and the titles will build up, and up, and up. Save and open in Shrink. But the size won’t increase, of course, because the cells are reused.