Valued functions are the lens through which we naturally perceive reality, the structure that we subordinate our perceptions to and seek to act on.
Unvalued functions are the aspects of reality that we take for granted or assume, things that operate as natural "behind the scenes" contexts or operations; they are implicit when using our valued functions.
For instance, Se perceives the world as discrete objects, each physical thing denoting its own tautological existence as the psychic emphasis of the observer. But in order to perceive things through the lens of Se, we assume that, within this object, certain processes operate that give it continuity or substance. Thus, perceiving the physical world as objects assumes or takes for granted that certain physical processes underly its existence. Conversely, perceiving the world through Si, physical fields, assumes that the interactions and processes take place between discrete objects which are assumed to occupy and compose the field.