What was the story behind Baba asking Shama for fifteen rupees Dakshina, and what was Shama's response?

Towards the end of the narrative in Chapter 18, a gentleman named Madhavrao comes to Shama with a specific message from Sai Baba. Baba had instructed Madhavrao to go to Shama and collect fifteen rupees as Dakshina. The instructions were very direct: Madhavrao was to get the money and return. Upon hearing this, as Chapter 18 recounts, Madhavrao was extremely surprised. Instead of producing the money, Shama gave a clever and devotional reply. He told Madhavrao to go back and offer his 'namaskar' (a respectful salutation) to Baba, stating that this was his form of Dakshina. Baba had also told Madhavrao to sit and talk with Shama, indicating the interaction itself was part of the divine play.