From what I understand, the show already ended on JTBC after two 120-minute episodes. However, the OTT platforms which released six 40-minute episodes so far (Coupang Play, Viu) will release two additional episodes in September (these special episodes will also be available on JTBC's YouTube channel).
I thought this show had only 10 Episodes but when did this become 12 ?
I think that the show was always supposed to be 12-episode long, but an editor must have assumed there would be only 10 episodes since other JTBC shows have the same format and the network never announced that Sea of Hope would run for 12 weeks.
I think that TVing releases all episodes at once like streaming platforms such as Netflix (at least, that was the case for TVing's "Scripting Your Destiny" back in March).
Source: https://www.hellot.net/mobile/article.html?no=81569