530 is the chain pitch, which equates to 5/8". 100 is the number of links. Links will always be represented as an even number and you can always buy a longer chain than needed and remove as much as needed to get the length required for your bike. A chain breaker that you can buy at most motorcycle accessory shops works well for this, but you can also grind off the head of a link pin with a dremel and shorten it that way. A breaker just forces the pin through the hole without cutting off the head.