I recently got a used G23 with 2-13 round mags. On the top of one follower is a "3" and on the other is a "4". Is there any meaning to these numbers? Both followers have "40" also (the caliber). Also, is there any difference between the followers for 13 round and 10 round mags? If I replace the 13 round follower with a 10 round one, will this limit the mag to ten rounds? I plan to move to Kalifornia, and can't have 13 round mags there. Thannks for any help.