A "full ride" includes tuition, fees, books, housing, and meals. Those things total 1.0 scholarship.
I only learned recently that the housing and meals portion may be taxable. So if they're going to give you a 20% scholarship, I would guess you'd want it applied to the tuition, fees, and books and not to the housing and meals.
In an interesting twist, the California legislature is playing with a law that would require California universities to include some incidental expenses as well (such as toothpaste and travel to/from college). This would be in violation of NCAA rules, and so the schools and NCAA are fighting it. But if California moves ahead with it, it could change things for college athletics as a whole as the NCAA would be greatly damaged without the participation of California schools. That was just and aside - sorry for the divergence.