@jackslate See the omake ( https://mangadex.org/chapter/827840 ) for a sorta-explanation. It's the page of text right after the future sequence. Evidently these are either web or twitter or pixiv comics or something, hence "volume 1 chapters" only consisted of 1 page. Evidently the scanlator got a hold of the tanks and is going by the tank numbering now. (They probably need to go back and re-organise the pages into chapters for consistency's sake, but I guess that'd be kind of a pain in the ass)
THe chapter numbering is a bit confusing. I originally thought the scanlator skipped the first 9 chapters. So are we going by chapters in 10s? Ichigo69's explination still has left me a tad bit confused.