The number that you use does not have to be in any specific order, there are no rules on that. In fact you could use just all numbers like, 5864183964. That would be a valid string for the 64bit encryption. The only thing that you cannot do is use all zeros. That is not allowed, and really would not be very safe.

The only thing that the router cares about is that it has a key that it can build the encrytoion from.

If you would like I can go into a much deeper explination on this, but most peoples eyes would just glaze over. In fact I can already feel a few people going.