थेरे गणहरे गग्गे, मुणी आसी विसारए ।
आइण्णे गणिभाविम्म, समाहिं पडिसंधए ॥ १ ॥
The elder Garg was a learned monk, a leader of a group of disciples, endowed with the full virtues of a true teacher, and a diligent guardian of inner equanimity.
Elder Garg Muni is introduced here as a fully accomplished teacher — a stainless elder, a holder of a large community of monks, and a scholar versed in all canonical texts. The commentary notes that "sthavira" carries three meanings: one ordained for twenty or more years (dīkṣā-sthavira), one learned in the Sthānāṅga and Samavāyāṅga scriptures (śruta-sthavira), and one sixty or more years of age (vaya-sthavira). Garg Muni embodied all three. As a gaṇadhara, he held and guided a community of 500 disciples. Yet the most essential quality singled out here is his inner equanimity: he himself dwelt in perfect stillness and worked tirelessly to bring his disciples into that same stillness. A true teacher is not merely knowledgeable — he models the very state he is trying to cultivate in others. Garg Muni is presented as that ideal: learned, communal, and serene.
The simple version: Garg Muni was a wise, experienced elder monk who led 500 disciples and kept his own mind perfectly calm and steady.