Bhagavad Gita, Chapter 11, Verse 2

Of You, O lotus-eyed, I have heard at length, of the origin and dissolution of beings, as also Your inexhaustible greatness.

Understanding is described here as something built up piece by piece, not arriving all at once.

Arjun names exactly what he's absorbed, how beings come and go, and what stays eternal, showing real, specific listening rather than passive agreement. That groundwork is what makes the next request possible.