These filter what this page and your Season digest surface. Deadline warnings that can cost a seat are never filtered out, whatever you set here.
The watcher checks all 20 portals every ~3 hours, around the clock — a result PDF that drops at 1 AM is caught by the 2 AM run, and a deadline that closes overnight is exactly the ping you want. Dated-milestone reminders (“tomorrow: R1 result”) ride the morning run only.