Clarification on Premium Chapters: Turning

Hello. 

Not sure where I should ask this so I'm posting here. 

I'd like a clarification on Premium Chapters for the novel "Turning".

I don't remember which chapter it was when the translation was taken over from Novelingua. But there was a note at the start that said that all chapters from that point would be premium content. However, they'd become free 24 hours after release for all to enjoy.

I assumed that that'd apply only to newly released chapters. But to my surprise, starting from chapter 1243,all chapters have to be bought with 10 coupons. Did I perhaps misunderstand? If so, can anyone explain please?

Also, if I were to buy a 30 day membership premium pack, would that unlock those chapters or would I still need to use coupons to unlock them?

I apologise if this is inappropriate or has been asked before. I'm new to the platform 😅

Thanks in advance.