In my experience, the breaks I schedule are merely a guide. I can never say exactly in advance how long it will take, for example, to get a drink or a meal. For planning purposes, it’s useful to be able to make an estimate, which gives you a rough finishing time.
But once you’re on the road, it becomes tricky, and you’d have to stick strictly to the times you’ve entered.
When I’m driving, I just try to keep an eye on the estimated finish time. That tells me how much time I’ve got left for a pause.
But perhaps it would be a good idea, if possible, to add an extra button for an ETA that includes pauses