A picture is worth a thousand words. Or, in this case, negative one thousand words.
On investigating, it appears the index for every card has set itself to -1, which probably has something to do with it.
I have no idea how this could have happened; it was fine before I headed off for the night, and was broken when I logged in again about an hour later. The later login was on mobile, but I’m currently back on a desktop, and the issue persists on both platforms.
-1 is the default for the index, and all of my self-made cards have that, so I don’t think that’s relevant. That’s pretty interesting about the negative lessons though. 
Woah! That’s definitely not supposed to happen. Did you hibernate the whole deck? It looks like it made some duplicate hibernation documents in the database.
The changes I’m deploying on Sunday will completely change the way this works so that should fix the problem. But for now I’ll set it back to normal. Sorry about that!
Your deck should be fine now, I’ve deleted all the duplicates. Sorry for the inconvenience.
Regarding the index, by default it is at -1 unless explicitely set (and having lesson sorting set to index-based). So you can pretty much ignore it. I might make some visual changes to hide it when it’s not set 
Thanks, @Neicudi: I no longer have negative reviews.
There’s a strange, new problem now, though: two of my five “new” lessons for the day are cards I’ve already learned. (They’re actually at level 2.) Stranger still, these lessons can’t be completed: in the lesson quiz, on correctly completing the second of two siblings, I can hit enter and get confirmation of a correct answer, but it won’t go on to the next quiz question. Usually a card would be marked as “learned” at this point and move to reviews, but here, it just gets stuck. The cards can be hibernated from the lesson queue – and sure enough, this ends up hibernating the level 2 card – but awakening the card puts it right back in the lesson queue, and it still can’t be completed.
Moreover, my homepage says I have 17 lessons, but I really only have two (the cursed two mentioned above.)
Hopefully the Sunday update fixes this, too, but I figured I’d let you know in case this is heretofore unseen behavior.
Sounds like the problem still is not completely fixed (it still seems to have duplicate progress documents for you somehow). I’ll get it fixed right now. Sorry again!
Okay @Pygmalion, it should really all be good now. I only saw one card with actual progress on it during the remaining two lessons session though, but just to be sure I’ve manually checked all of them. Sorry for the wait, it was a pretty difficult bug to track down.
I think the lesson count on the homepage being off is because you added a new deck, which defaults to 15 lessons a day. But due there being no cards yet, it should be at 0. I’ve also changed the logic behind this calculation with the update for tomorrow though
@Neicudi you’re right: setting the new lessons count on the empty deck to 0 fixed the homepage count. Everything else appears to be working, too. Thanks for your help – keep up the good work!
