CC Madhya 7.37
jala-pātra-bahirvāsa vahibe kemane
From this verse it is clear that Caitanya Mahāprabhu was chanting the holy names a fixed number of times daily. The Gosvāmīs used to follow in the footsteps of Śrī Caitanya Mahāprabhu, and Haridāsa Ṭhākura also followed this principle. Concerning the Gosvāmīs — Śrīla Rūpa Gosvāmī, Śrīla Sanātana Gosvāmī, Śrīla Raghunātha Bhaṭṭa Gosvāmī, Śrīla Jīva Gosvāmī, Śrīla Gopāla Bhaṭṭa Gosvāmī and Śrīla Raghunātha dāsa Gosvāmī — Śrīnivāsa Ācārya confirms, saṅkhyā-pūrvaka-nāma-gāna-natibhiḥ. (Ṣaḍ-gosvāmy-aṣṭaka 6) In addition to other duties, Śrī Caitanya Mahāprabhu introduced the system of chanting the holy name of the Lord a fixed number of times daily, as confirmed in this verse (tomāra dui hasta baddha nāma-gaṇane). Caitanya Mahāprabhu used to count on His fingers. While one hand was engaged in chanting, the other hand kept the number of rounds. This is corroborated in the Caitanya-candrāmṛta and also in Śrīla Rūpa Gosvāmī’s Stava-mālā:
badhnan prema-bhara-prakampita-karo granthīn kaṭī-dorakaiḥ
saṅkhyātuṁ nija-loka-maṅgala-hare-kṛṣṇeti nāmnāṁ japan
hare kṛṣṇety uccaiḥ sphurita-rasano nāma-gaṇanā-
Therefore devotees in the line of Śrī Caitanya Mahāprabhu must chant at least sixteen rounds daily, and this is the number prescribed by the International Society for Krishna Consciousness. Haridāsa Ṭhākura daily chanted 300,000 names. Sixteen rounds is about 28,000 names. There is no need to imitate Haridāsa Ṭhākura or the other Gosvāmīs, but chanting the holy name a fixed number of times daily is essential for every devotee.