I do design and tech support for industry. Official hours are 7,5h/day (lunch is off-duty). 3 days in office 2 days remotely. My actual workload varies a lot. If everything works and all resources are in use, I might not have anything to do for weeks on end. If shit hits the fan, I'm on overtime working 10h days, using every second.
I might quess that on average 2h/day of actual work and varying part of this are communally beneficial activities I invent for myself to keep myself busy.