Can you explain the interpretation of the Bhagavad Gita verse mentioned in the text and how it relates to knowledge and ignorance?

Chapter 50 discusses a verse from the fourth chapter of the Bhagavad Gita: "Tadviddhi pranipatena pariprasnena sevaya | upadeksyanti te jnanam jnaninastattvadarsinah ||". The text presents a subtle interpretation, suggesting that an 'Avagraha' (a linguistic symbol) appearing before the word 'Jnana' (knowledge) in the third line acts as an indicator of 'Ajnana' (ignorance). This implies that before one can be instructed in true knowledge by the wise, one must first understand and address their own ignorance. This interpretation sets the stage for the chapter's broader discussion on the contrast between 'Vidya' (pure knowledge, like 'I am Brahman') and 'Avidya' (the ignorant attitude of being a sinner).