Can you explain the philosophical point Chapter 50 makes using the 'Avagraha' in the Bhagavad Gita verse?

Chapter 50 delves into a subtle interpretation of a verse from the fourth chapter of the Bhagavad Gita. It explains that the presence of an 'Avagraha,' a specific linguistic symbol, before the word 'Jnana' (knowledge) in the verse's third line changes its meaning to indicate 'Ajnana' (ignorance). This implies that the verse could be an instruction on understanding ignorance first. The chapter highlights this to emphasize a key principle: one must first understand and remove ignorance to purify the mind, after which true, infinite knowledge can manifest. This is presented as a necessary step before one can attain non-dual Samadhi.