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Oh, got it.
BTW, that constraint's documentation is missing, it would be helped me a lot 

Thanks for your replies!
But it take so much time to run and now impossible.
How about "Min hour daily for a (all) teacher(s)" could take one more argument that decide exactly day to apply min hour (in my case is Monday and/or Friday)?

Thanks, I will try it

I don't know how to call that constraint, below is description:
In my country (VN), primary, secondary and high school has a subject that always start at first hour of Monday (and some has a subject that always start at the end of Friday). That (two) subject(s) of each class is teaching by one teacher (called GVCN in my country).
Everything work fine but now I have problem with that: some teacher (GVCN) has only one activity on Monday (same on Friday).
I want prevent that by adding a constraint to have at least 2 or more activities of selected teacher (GVCN) on Monday (and/or Friday).