"The word ātmā refers to all the different expansions of the Supreme Personality of Godhead. One of them is the Supreme Personality of Godhead Himself, Kṛṣṇa, and the others are different incarnations or expansions of Kṛṣṇa.
The word ātmā also includes all kinds of Bhagavān, the Supreme Personality of Godhead. This means that Kṛṣṇa has unlimited expansions. This is described in Brahma-saṁhitā (5.46):
dīpārcir eva hi daśāntaram abhyupetyadīpāyate vivṛta-hetu-samāna-dharmāyas tādṛg eva hi ca viṣṇutayā vibhātigovindam ādi-puruṣaṁ tam ahaṁ bhajāmi
These expansions are thus compared to candles that have been lit from an original candle. All the secondary candles are equally powerful, but the original candle is that from which all the others have been lit. Kṛṣṇa is the original Supreme Personality of Godhead, and He is expanded as Balarāma, Saṅkarṣaṇa, Aniruddha, Pradyumna and Vāsudeva. In this way there are innumerable incarnations and expansions who are also called Bhagavān, the Supreme Personality of Godhead.