Chanting 64 rounds Harināma daily!
Srimad Bhagavatam: 6.3.31:
Śukadeva Gosvāmī continued: My dear King, the chanting of the holy name of the Lord is able to uproot even the reactions of the greatest sins. Therefore the chanting of the saṅkīrtana movement is the most auspicious activity in the entire universe. Please try to understand this so that others will take it seriously.
Srimad Bhagavatam 12.3.51:
My dear King, although Kali-yuga is an ocean of faults, there is still one good quality about this age: Simply by chanting the Hare Krsna Maha-mantra, one can become free from material bondage and be promoted to the transcendental kingdom
One Maha Mantra = 16 names of the Lord – 3 transcendental words of Hare, Rāma and Kṛṣṇa.
One round in a japa mala =108 Hare Kṛṣṇa Maha Mantra= 1728 names of Krishna.
16 rounds = 27,648 names of Krishna
64 rounds = 110,592 names of Krishna
Caitanya Bhagavat (by Sri Vrindavan das Thakur) – Antya Khanda – chapter 9 verses 116 to 125:
When brahmanas invited Lord Caitanya Mahaprabhu to take a meal:
Caitanya Mahaprabhu: the Lord smiled and said, “First you should become a laksesvara “I take meals only in the house of a laksesvara.” Hearing this, the brahmanas became worried. “Do you know who is a laksesvara? He is someone who daily chants a hundred thousand holy names. “I call that a person a laksesvara. I take meals in only such a person’s house, not in the houses of others.”
Brahmanas replied: “O Lord, we will chant a hundred thousand names. Please therefore take Your meals in our houses. It is our good fortune that You are teaching us in this way.”
Srila Prabhupada discovered that his disciples from the West could not chant 64 rounds so he reduced the chanting to 32 rounds, but when he found out they could not chant even that he told them 16 rounds minimum.
Today some members think that this is the maximum but these 16 rounds was only to start you into the process of chanting with the understanding that as you get the taste for the holy names which is the sound vibration of the Lord and non-different from Him, you would gradually increase from 16 rounds to 64 rounds.