CC Madhya 6.78
bhagavattā-lakṣaṇera iṅhātei sīmā
“My dear Bhaṭṭācārya, you do not know the greatness of Lord Caitanya Mahāprabhu. All the symptoms of the Supreme Personality of Godhead are found in Him to the highest degree.”
Since the Bhaṭṭācārya was an impersonalist, he had no idea of the Absolute Truth beyond the impersonal effulgence. However, Gopīnātha Ācārya informed him that Caitanya Mahāprabhu was the Supreme Personality of Godhead. Those who know the Absolute Truth know it in three phases, as explained in Śrīmad-Bhāgavatam (1.2.11):
brahmeti paramātmeti bhagavān iti śabdyate
“Those who are in knowledge of the nondual Absolute Truth know very clearly what is Brahman, what is Paramātmā, and what is the Supreme Personality of Godhead.” The Supreme Personality of Godhead is ṣaḍ-aiśvarya-pūrṇa, complete with six opulences. Gopīnātha Ācārya emphasized that all those six opulences were completely existing in Śrī Caitanya Mahāprabhu.