People with office jobs - how long do you actually spend working?

I've recently started a new job a few months ago, it's my first office job and I'm in the HSQE department. I feel like I spend too much time doing nothing at my desk, but I have no idea what to do instead. I spoke to my boss and he told me not to worry and I'm doing fine. Is this normal for office jobs? If I totaled up all the time where I'm actually doing a task, it's probably like 2-3 hours of my day.