multikill/deathnote achievement issue

[Zio]

First off, I wish the "per tier" got scrapped from descriptions because it's not working like that. None of them add their multiplier PER tier, it's just that one multiplier that's added to the final value.
As for the bug, I just went and did lavathian skulls but somehow I needed more kills, I don't remember how many kills were necessary to advance before the update (though I think it was way more than just one million) but I've been through everything with all characters and farmed the cards for a while, but I still needed to kill 95 million on my main character for the skull. Plus, I got the in-game achievement even though I was still missing one, but I did have the 1 billion skull already on the last one so the achievement only seems to track all levels of skulls rather than just the lavathian