What specific challenge did Das Ganu face while working on the Ishavasya Upanishad, and what was Sai Baba's unusual advice to him?

According to Chapter 20, Das Ganu was composing a Marathi commentary on the Ishavasya Upanishad, titled "Ishavasya-Bhavartha-Bodhini." Although he translated the text word for word, he struggled to grasp its deeper, internal secret, and his mind found no joy in the work. This Upanishad is described as being full of deep meanings. When Das Ganu took this doubt to Sai Baba in Shirdi, Baba gave him a very peculiar instruction. Instead of explaining it himself, Baba told him, "The resolution of this doubt of yours will be done by the maidservant at Kaka’s house when you return there."