)
that number is more then just a reference, and not only that it's a reference to "hitchhiker's guide to the galaxy" movie, and could also mean that twilight represents unity for all intelligent beings, to give friendship to all that are willing to accept, also she has the number ever since she got her CM, it has 7 stars in total(even the white one behind it) and each is like a hexagram (meaning a 6 pointed star), and if you multiply 7 withby 6, you'll get the same number as that there.