TMDb always try to follow the original release. So, in this case, the episodes match the release on Naver.

If they follow the original release, it should be 10 episodes. For they were originally released by naver on the internet as 10 episodes (but each episode was divided into two parts, and only 10 episodes of the 20 came out). A month later it was released on kbs2 as 20 episodes (single episodes). And Netflix has released 10 episodes (two episodes in one, which makes 20 in total). Naver and Netflix released it as 10 episodes, but on Netflix the episodes are double, i.e. twice as long, because as I said above, they haven't released all the episodes on the net and the edition itself is completely different.

You've added 20 episodes with the dates of the 10 naver episodes, which means that some episodes also have the wrong dates. Note: In the three releases, the episode orders are different.

You should have all 3 versions.

1. The original naver (web) 10 episodes
2. kbs2 alternative version (tv) 20 episodes
3. Netflix 10 episodes (double episodes)

Or having only the last two and not having the naver, because there are 10 episodes left.

here are the names and dates of the two Korean versions. namu korea

And currently the names of the English episodes don't match the names of the Korean episodes. The best thing would be to create everything from scratch with all 3 versions.

Excel with 3 versions