The augment num is added to labh 'to get' preceded by upa before ya when the reference is to something praise-worthy.,
As उपलम्भ्या भवता विद्या, उपलम्भ्यानि धनानि ॥ These words are formed by ण्यत् and have svarita on the final. Why do we say 'when referring to something praise worthy'? Observe उपलभ्यमस्माद् वृषलात् किंचित्, this is formed with the यत् affix 3.1.98.,