CC Ādi 5.74

tāṅra eka svarūpa — śrī-mahā-saṅkarṣaṇa
tāṅra aṁśa ‘puruṣa’ haya kalāte gaṇana
Word for word: 
tāṅra — His; eka — one; svarūpa — manifestation; śrī-mahā-saṅkarṣaṇa — the great Lord Mahā-saṅkarṣaṇa; tāṅra — His; aṁśa — part; puruṣa — the Mahā-Viṣṇu incarnation; haya — is; kalāte gaṇana — counted as a kalā.
Translation: 
Balarāma’s own expansion is called Mahā-saṅkarṣaṇa, and His fragment, the puruṣa, is counted as a kalā, or a part of a plenary portion.