JoanB The total word count of the story by the end of the contest period has to be at least 10000 words for it to qualify. For individual chapters, there isn't a specific length requirement, but Webnovel recommends at least 800 words each.
As for #63, I don't see it as a single chapter = the whole story, but rather that like how one keeps a diary and writes in it everyday, the "one chapter challenge" is actually a write "one chapter per day" challenge. So, you have to post everyday like you're writing a diary, blog, poem, song, essay, or short story, etc.