(By David Gil): "in many ... languages, nouns in construction with numerals may occur with an additional grammatical element even when such nouns are of high countability... Such elements are typically referred to as sortal numeral classifiers. This term makes reference to one of the most salient functions of such forms, which is to divide the inventory of count nouns into semantic classes, each of which is associated with a different classifier."
The dataset concerns only "sortal numeral classifiers" (not "mensural numeral classifiers"), which correspond to the Grammaticon's "numerative".