It's not about getting things done, it's about feeling accomplished while you're doing them. The 240-minute rule is simple: work on a task for exactly 240 minutes, no matter what. After that, take a 10-minute break, then return to your task.
This is not a time management technique, it's a sanity preservation technique. You'll get more done, but you'll also have more time for cat videos.
Learn about the benefits of Break Time Advantages or Discover how to overcome The Siren Song of The 60-Minute Rule