I'm not sure why those are important to the cycling community, the first one is somewhat interesting though. Apparently if you subtract the two digits of a number from the number itself as they instruct, the answer will always be a multiple of nine. If you want to really impress your friends just go to that site, say you don't have to do the math, you are just going to choose, say, 72, and it will work. Then try it again and use 54, etc.