The numbers are likely ascending, but they are almost definitely not sequential, meaning not every number is used, they'll skip some numbers. The way Breguet makes their numbers is a bit of a secret, as it is used to prevent counterfeiting watches and prevent the introduction watches with fake serial numbers. Thus, I cannot say much more. I do not know if they skip numbers in a set mechanical pattern or if it's somewhat random. I have the presumption that it's somewhat random.