By the way, High School Family also hits chapter 8 due to having the first two published in the same issue. Do you need 7 chapters or 7 weeks to get your first ranking?
It's 7 issues, because it should usually take around 7 weeks between making the ToC for the issue where chapter 1 appears and getting the reader poll results. Here's a rough estimate how the process might look like and how long it might take. The 3 chapters in advance part was mentioned in Bakuman iirc.
Week 0: ToC placement for the issue of chapter 1 is decided (mangaka is already working on chapter 1).
Week 1: The mangaka finishes chapter 1 and maybe already starts work on chapter 2 due to the increased length.
Week 2-4: Mangaka continues creating chapters on a weekly basis (usually about 3 chapters in advance).
Week 5: The issue with chapter 1 gets released on Monday in Japan while the mangaka starts his/her work on chapter 5. Readers can vote for chapter 1 in the reader polls.
Week 6: Chapter 2 releases, while the poll for chapter 1 is over and the results are counted.
Week 7: ToC placement is decided for the chapters that are created in week 8, partly based on the reader poll results they got in the previous week.
Week 8: Mangaka starts working on chapter 8, which is the first chapter where the ToC placement is affected by reader polls.
In case of Highschool Family, the first two chapters were released in the same issue. So the mangaka was working on chapter 9 by the time they get the reader poll results. This means that it should get its first rank when chapter 9 releases. Everything on top is an estimate btw, so I might be off by a week somewhere or I might've missed something else that takes away a lot of time. But getting the reader poll results for chapter 1 of a manga should happen shortly before they create the ToC for the issue with chapter 8 of that same manga, assuming the new manga only got one chapter per issue.
