The grammar approx.grm defines a phrase type, APPROX, which is used in quantity-p.grm to modify words that describe exact quantities of things so that they describe only approximate quantities.  Examples are "almost exactly" in "almost exactly two hundred" and "not quite" in "not quite half".   The same phrase type is used in npcomponent.grm as a pre-determiner (PRE-DET), in phrases like "almost exactly the amount of water" and "not quite my salary".