Bhagavad Gita, Chapter 15, Verse 19

He who free from delusion thus knows Me, the Highest Spirit, he knowing all, worships Me with all his heart, O descendant of Bharata.

Real, complete knowledge is defined here specifically, knowing this one thing without doubt, not accumulating endless information.

Krishna ties full understanding to a single, real recognition rather than a broad collection of facts. Whole-being worship is named as the natural response once that doubt is actually gone.