That's not random.. it just sends a cart in a loop till you press a button and then it stops on a spot giving you a number. So if you put a cart in the system and hit it exactly at 8seconds you'll always get the same number. Besides that it requires you to manually remove the cart.. not exactly what I'd call a good "random" generator.
Take a look at this design for a random number generator. This is pseudo random using torch burnout to generate a random output state. You hook multiple of them together and feed the random outputs into a binary decoder. Nice job though.