That is a slightly different setting to pause a whole topic, not hide an individual post.
The hide post setting they are talking about I believe is “hide post sensitivity,” default for which is “medium.”
There may not be a specific number of flags listed for that because depends on who makes the flag report, a flag from a TL3 has a lot more weight than flag from TL1 user. In fact looks like only one TL3 flag (edit: flag of spam only of new user post) is enough for post to be hidden until mod review with default settings:
There are quite a few various settings that can be adjusted for the flag system.