SB 1.3 - The countless and the not so well known incarnations
The incarnations of the Lord are innumerable, like rivulets flowing from inexhaustible sources of water. The Lord manifests as many incarnations as there are species of life to maintain the faithful and to annihilate the faithless. The Lord incarnates as Lord Caitanya in Kali yuga in the garb of a devotee. All incarnations are distinguished by specific extraordinary feats which are impossible for the living being to perform. Some incarnations mentioned above are plenary portions of the Lord. The Kumāras are empowered with transcendental knowledge, Nārada with devotional service, Pṛthu with executive function and so on. The Matsya incarnation is a plenary portion.
The word asaṅkhyeyā means not countable. However, there is another meaning: not well known (asamyak khyāta). Some like the puruṣāvatāras are well known. Others are not so well known. Prahlāda confirms in SB 7.9.38 that the Lord appears covered (channaḥ) in Kali yuga and so is not well known. This indicates Mahāprabhu.
After listing the avatāras, the vibhūtis of the Lord are enumerated as the sages, Manus, devatās, powerful humans (sons of Manu) and Brahmā’s sons, the Prajāpatis.