Hey there! The cards you’re missing are the ones that were either duplicates or extra clozes that have been now removed to improve card quality. Rest assured you have right amount of cards under the AnKing_v12 deck. You can go ahead and delete the cards under the v9 tag if you want to (you can keep the ones you’re actively doing if you want to but they will mostly be duplicates). Also look under the AnKing_v12::DELETE(Duplicate) tag, you can also delete them.
If you ever feel you’re missing something or have accidentally deleted something, you can go in the browser > ankihub > reset local changes to a deck > AnKing_v12
That will restore any cards from the v12 that you might ever delete accidentally.