you can't really account for academic time on a hours-per-week basis. there's too much variety. as others have noted, it's a modal way of working. one week it's this, next month it's this, then maybe there's a paper deadline so you have to crunch down and get on a particular project. maybe it didn't fly so you have to try something else. it also depends where your university is.

being a professor is like running a company but with fewer support staff.

running your lab takes time most weeks, it's almost a constant: whole-lab meetings are easily 2-3hours per week, meeting each individual member of your lab is another hour or so each. then there's the admin for your lab (some of which you delegate). then there's organizing new grants: this involves collaborating with other people which means... yup, more meetings, often over skype or similar. then working out ideas, then writing, re-writing, and re-writing the draft and doing a lot of preliminary work. many grants need a lot of preliminary work to be shown before they get funding.

teaching is a lot more than just lecturing, you forgot: time spent talking to students one-on-one, running labs, designing interesting homeworks and exercises, preparing exams, marking homework and exams (marking easily consumes a week or two per course here).
also, "knowing stuff already" doesn't mean you can teach it. it's enough to teach yourself, not others. developing a new course or just keeping and old course up to date and interesting takes an awful lot of time. what content will you include? what exercises? what text books? what's examinable? what's useful? what's the structure? what can students handle? all of these apply to courses old and new, but are faster for older courses, especially ones that do not change much (i.e., not active research areas).

then there's your research. what you do here depends upon the stage of you career. in the very least, you need to read. a lot. in CS-disciplines, this is easily a weekly activity. then you can spend some time thinking. then trying some things out. maybe. then going to conferences, talking to more people. presenting your own work: writing papers, arguing about their acceptance, visiting labs, workshops and conferences to give talks, preparing talks, etc.. believe it or not, you have to advertise and advocate your research, even once it's published and done. how else will people notice? so advertising is another thing you must spend your time on.
now multiply all this work by the number of projects you have: potentially one per lab member.

interestingly you miss out one of the most important parts of being an academic--reviewing other people's work for conferences and journals. this takes a lot of time. firstly because reviewing a paper thoroughly takes considerable time, secondly because the discussion afterwards takes considerable time, and thirdly because often you will do this many, many times a year. as you become more senior, you take on a more senior role here: managing reviewers, journal and proceedings, conferences and workshops, etc.

i'm sure this isn't the same everywhere, but this is a small glimpse at academia in the places i'm aware of. it's busy busy busy.