Hey Rami,
I agree - it varies from place to place! And, Steve is right that menu affects labor as well.
May I suggest that you move managers and other salaried employees out of COGS and to overhead. Those costs are fixed and don't change. Which means the associated percentage for salaries will vary widely every week. Instead, I would suggest trying to get an hourly labor % target, as that's they way they'll manage labor when they're open.
At out place, we make everything from scratch except the pasta noodles and sandwich bread. As a result, our BOH labor is 2/3 of our total hourly labor. Also, we're not full-service, so all of our staff is full-wage, rather than tipped. Our weekly target is 22.5%, and we usually beat it by a point or two on the month. (Note that this % is hourly labor only.)
When we were working on our business plan, we made some sample schedules for busy weeks and slow weeks, and costed them. We took the average as our ballpark labor %. (Our business plan had 25%).
Hope this helps!