Kenny, every series has there own numbering system, if you race MSC they give you a # NETRA, same thing, ECEA, same thing. Alot of the time it is linked to the class you are in or your level of riding ability. In MX Black plates with white # is Novice, Yellow and black # would be amature and white plate with black # would be expert. If you get a MSC # they ask you your birthday or something else like your address and give you that #. Find the series you think you will race in and then see how they do it.