Red Book 12 follows the permanently assigned numbering system utilized since Red Book 6, with some well thought out exceptions made for clarity and better organization. Jar collectors still argue about the changes between the 6th Edition and the 7th. I see the point, it is hard to memorize new numbers and hurts ever time you have to deal with the fact that old 500 is now something else, but get over it. There might be more to the story, go to a Jar Show and ask around!
It can be a little tough finding your jars sometimes. There are many many minor varieties of some jars. I find that it is mostly alphabetical by brand name or what is said on the jar, start with the word that uses the biggest font or the brand name and work from there. Unmarked jars are of course the hardest to find, but stick with it and soon you will begin to recognize the tip-offs to different brands of jars.
“The fruit jar changed America. The Red Book changed fruit jar collecting.” – Charles Strusz, hobbyhomebrew.com, 2019
“A hundred and fifty years ago, these jars meant survival,” – Authenticity, Repurposed, in a Mason Jar – NY Times