How did Sai Baba test Shama by sending a messenger to ask for fifteen rupees in Dakshina, and how did Shama respond?

In a curious event described in Chapter 18, Sai Baba sent a messenger to Madhavrao Deshpande (Shama) with a very specific command: "Take fifteen rupees as Dakshina from Shama." The messenger was also instructed to sit and talk with Shama for a while before returning. Upon hearing the request, Shama was extremely surprised. Instead of providing the monetary Dakshina, he responded by telling the messenger to convey his 'namaskar' to Baba as his form of Dakshina. The messenger accepted this unconventional offering, noting that "fifteen namaskars were received," and then urged Shama to come and speak with Baba, demonstrating a unique interaction and test between Baba and his devotee.