Why did Madhavrao (Shama) question Sai Baba regarding the two gentlemen from Goa?

In the account from Chapter 36, Madhavrao, also known as Shama, was present when two gentlemen from Goa came for Sai Baba's darshan. He witnessed Baba ask for and accept fifteen rupees as Dakshina from one visitor, but then immediately reject an unsolicited offering of thirty-five rupees from the second visitor. Seeing this apparent partiality and the surprising rejection of a larger sum, Madhavrao was puzzled and decided to ask Sai Baba to explain the seemingly inconsistent behavior, which had surprised everyone who was there.