• ātmā — the Self (Paramātmā)
  Here specifically Paramātmā — the Supreme Soul, not the jīva-ātmā. Gauḍīyas read the verse in the bhāgavata frame: Paramātmā is Kṛṣṇa's Mahā-Viṣṇu/Garbhodakaśāyī expansion.
• svayam-jyotiḥ — self-luminous
  Compound: svayam (by Himself) + jyotis (light). Bhagavān shines by His own light; He needs no second source. Upaniṣadic vocabulary (Bṛhad-āraṇyaka 4.3.9), now spoken by Kṛṣṇa about Himself.
• nirguṇaḥ — free from material qualities
  Compound negation: nir + guṇa. Bhagavān is nirguṇa in the sense that the material guṇas do not touch Him; He is not nirguṇa in the sense of being attribute-less. Gauḍīyas: His sac-cid-ānanda qualities are aprākṛta, transcendental.
• ātma-sṛṣṭaiḥ — created by Himself
  Compound: ātma (self) + sṛṣṭa (created). The guṇas are not external to Him; He emanates them. The multiplicity He appears in is generated by His own creative act.
• bahudhā īyate — appears as many
  Adverb + verb: bahu-dhā (in many ways) + √i (to go, to seem). Echoes Kaṭha 2.1.10: nehā nānāsti kiñcana. The 'manyness' is appearance; the One is the reality — but neither side is unreal.

• Bhanu Sw SB 10-85-24-26 - Bhagavatam is like Krsna which manifests differently for different types of people - ISKCON Chennai
  His Holiness Bhanu Swami· English

One lamp behind colored glass casts blue, red, green light across the wall. The lamp is one; the colors are many. Paramātmā is one self-luminous Person; the modes are the glass; the apparent multiplicity is what the wall sees.