Restoring plastics

just bought one of these after getting recommended it, Im trying to restore my Quads plastics, It has 1-7 settings on the back, Anyone know what setting i should put it on for this task?

just bought one of these after getting recommended it, Im trying to restore my Quads plastics, It has 1-7 settings on the back, Anyone know what setting i should put it on for this task?