It means that in Factory Division, your shotgun cannot have the capability of holding more than 8 rounds. You either have to use a shorter extension tube, or you have to plug it.
Production Division states that you have to start with 9 rounds in the gun, but can have a longer extension and are allowed to put in more rounds after the buzzer goes off. Like you could before.
Unlimted has no capacity limits at the start buzzer or after. (for shotgun)
Looking over things, the only changes I saw to TI, TO, and Open (other than the name change), was to TI (now Factory). I may have missed something, but didn't see anything. Heavy did change, and they added pistol caliber rifle divisions. Pistol caliber rifle division allows 5.7's. Would be cool to see some P90's. Also, in pistol caliber rifle, you can shoot all paper and steel with the rifle. Only targets you can't shoot with it are clays.