It is clearly mentioned here (in SB 3.28.12) that one has to meditate upon the expansion of Visnu. The word kastham refers to Paramatma, the expansion of the expansion of Visnu. Bhagavatah refers to Lord Visnu, the Supreme Personality of Godhead

Expressions researched:
"It is clearly mentioned here that one has to meditate upon the expansion of Viṣṇu. The word kaṣṭhām refers to Paramātmā, the expansion of the expansion of Viṣṇu. Bhagavataḥ refers to Lord Viṣṇu, the Supreme Personality of Godhead"

Srimad-Bhagavatam

SB Canto 3

It is clearly mentioned here that one has to meditate upon the expansion of Viṣṇu. The word kaṣṭhām refers to Paramātmā, the expansion of the expansion of Viṣṇu. Bhagavataḥ refers to Lord Viṣṇu, the Supreme Personality of Godhead. The Supreme Godhead is Kṛṣṇa; from Him comes the first expansion, Baladeva, and from Baladeva come Saṅkarṣaṇa, Aniruddha and many other forms, followed by the puruṣa-avatāras. As mentioned in the previous verses (puruṣārcanam), this puruṣa is represented as the Paramātmā, or Supersoul. A description of the Supersoul, upon whom one must meditate, will be given in the following verses. In this verse it is clearly stated that one must meditate by fixing the vision on the tip of the nose and concentrating one's mind on the kalā, or the plenary expansion, of Viṣṇu.

SB 3.28.12, Translation and Purport

When the mind is perfectly purified by this practice of yoga, one should concentrate on the tip of the nose with half-closed eyes and see the form of the Supreme Personality of Godhead.

It is clearly mentioned here that one has to meditate upon the expansion of Viṣṇu. The word kaṣṭhām refers to Paramātmā, the expansion of the expansion of Viṣṇu. Bhagavataḥ refers to Lord Viṣṇu, the Supreme Personality of Godhead. The Supreme Godhead is Kṛṣṇa; from Him comes the first expansion, Baladeva, and from Baladeva come Saṅkarṣaṇa, Aniruddha and many other forms, followed by the puruṣa-avatāras. As mentioned in the previous verses (puruṣārcanam), this puruṣa is represented as the Paramātmā, or Supersoul. A description of the Supersoul, upon whom one must meditate, will be given in the following verses. In this verse it is clearly stated that one must meditate by fixing the vision on the tip of the nose and concentrating one's mind on the kalā, or the plenary expansion, of Viṣṇu.