  Kochen-Specker (KS) theorem lies at the heart of the foundations of quantum
mechanics. It establishes impossibility of explaining predictions of quantum
theory by any noncontextual ontological model. Spekkens generalized the notion
of KS contextuality in [Phys. Rev. A 71, 052108 (2005)] for arbitrary
experimental procedures (preparation, measurement, and transformation
procedure). Interestingly, later on it was shown that preparation contextuality
powers parity-oblivious multiplexing [Phys. Rev. Lett. 102, 010401 (2009)], a
two party information theoretic game. Thus, using resources of a given
operational theory, the maximum success probability achievable in such a game
suffices as a \emph{bona-fide} measure of preparation contextuality for the
underlying theory. In this work we show that preparation contextuality in
quantum theory is more restricted compared to a general operational theory
known as \emph{box world}. Moreover, we find that this limitation of quantum
theory implies the quantitative bound on quantum nonlocality as depicted by the
Cirel'son bound.
