So the way it works actually is that it has nothing to do with the 7 days, nothing can be changed at the blockchain level. It's immutable ie unchangeable, when you edit a post, which you can do at any time on any post forever, you are editing it at the frontend level. So if someone built a frontend that just showed what was on that level and you edit a post and delete the data, it won't show up. But if someone who is technically savy REALLY wanted to see the original post they could because it's still there.