What I mean with focused work is only the time that you are working. Not counting the time you take a break, not counting the time you go to the bathroom, not counting the time you get up to drink water, etc. If you don't stop your time-tracker during non-work activities, please mention it.
I keep a log. If I was working and you called me, I would stop the meter, talk to you and start the meter again when I started working. If you were another client I would record my hours working for them. I have a log for every client. I did not stop the clock for bathroom breaks.
I have been scrupulously tracking focused time for years, since I was in college. I "stop the clock" when I sit back to daydream for a few minutes, check the news, or use the bathroom. I also generally don't include meetings unless they're small meetings where I need to be fully engaged.
The result is that for me about 150 minutes of real work feels like an ordinary productive day at my not overly demanding dev job. 180 minutes is doable on a daily basis but I have to be pretty disciplined. If I set my goal to 240 minutes work begins to consume my life and I often stay late to make it up. Days when I have done more than 5 hours of work by this definition are really rare, I either get so stuck on a problem that I am consumed by it (super rare) or have some really impending deadline that blots out everything else (rare). I know if I put in 240m I'm doing a really solid day's work every day.
In college while taking 18 credits of graduate courses I could get by on 4h studying/homework per day, but had to bump it to 5h near the end of the term.
But after that time I start to mix things up and make mistakes. So I really wish 6 hours were the actual work time... but in reality I have to work 8 hours a day.
I'm a solo dev now. I don't keep track of my time religiously but RescueTime reports I'm coding 3-4 hours a day plus 1-2 hours of email.