The original official episode names are just the episode number.

The title in English being just the episode number is only for the Netflix release. Netflix did not translate the titles.

Each episode with the exception of 8 and 12 have title cards in Japanese. Episode 7 had the title card show a title of 「　　　　　」which is equivalent to a bunch of spaces in quotes or a silence.

I do understand given Netflix is the original English release if those are the names TVDB choses to use.

As per our rules, the English titles should always be the titles used for the first official broadcast in an English speaking country. This first official broadcast is the Netflix broadcast. Consequently, the correct titles here are the episode numbers.