Setting Boundaries in Remote Work

My post title might be a bit misleading but I am really struggling to understand something since I have started working remotely.

A typical day at the office involves writing code, chatting a bit with co-workers, toilet breaks, and watching a Youtube video(or reading a blog) to relax a bit. All this happens between check-in and check-out and whatever you are doing is there for everybody to see.

Roughly, I would say these things take about an hour at the office and you code for about 7 hours.

However, in a work-from-home setup, you can be coding for 8 hours straight which I feel is very hard to do. This is because you can easily deduct the time you are spending on other things.

So, my question is what are the acceptable/implied rules that count as work-from-home and companies are usually okay with them?