Oh... Uh I'm not sure they have a meaning other than the number was already taken. Like when I ran the 6 hour I had a guy that always ran 57 but since I signed up before him he had to put 57xWhich one of us? For me I'm asking what the letter after the number stands for. Like 777x or 253H
Your amateur series makes you pick a unique number? What happens when over 999 people apply? Most districts in the States don't let you register your number and you just have to hope that no one else gets it in your area. Some districts do require you to use the last 3 digits of your AMA number though, others only recommend it.I can only speak for CMRC which is the Canadian sanctioning body. When you apply for your racing licence, you get to pick your number as long as someone doesn't have it.....Once you own a number, it's yours as long as you pay your licence fee by the designated date.