How can a game have both Full and Partial Controller suport?
It would appear that having both is an error in the entry at some point. According to the developer of Scourge:
"The game is fully suported, even the text input in Big Picture mode" [...] "Seams like an error." source
After looking through many of the Full controller support and Partial controller support games, it seems like this is a rare case. It is likely that any game that lists both did so by accident.
It can't, they are mutually exclusive. Whoever was entering the information made a mistake. You can ask on the game's forums whether it has full support.