You're understanding correctly, but what you're missing - the unknown to us x factor, is the line of submitted petitions since that 2009. The numerical limits on immigrant visas for preference categories are not something that changes. You have X number of them for F4 category, whoever is below the cutoff for issuance, gets in the line - and that line just keeps growing. Perhaps visa bulletin on state.gov would be of some help to get you some details? Just google visa bulletin November 2025 and from there you can go back see prior months issuances. I think they also break it down by preference categories, then by country.