For me, a Productive Hour means 60 minutes of uninterrupted deep work with a full focus on the given task. If I’m interrupted or just pause (answering team mate’s question, lunch, etc), then I’m stopping the timer for this task and track it as a “not-productive” time. My daily average for development is around 4.5 productive hours and I can push myself to do 8 - 9 hours when doing a less mentally demanding activity.