Can you explain the incident with the two gentlemen from Goa and their offerings to Sai Baba?

Chapter 36 of the Shri Sai Satcharitra recounts an incident where two gentlemen from Goa came for Sai Baba's darshan. Although they arrived together, Baba treated their offerings very differently. He specifically asked one of the men for a Dakshina of fifteen rupees, which the man gave with joy. However, when the second gentleman voluntarily offered thirty-five rupees, Sai Baba immediately rejected and returned the money. This action surprised everyone present, including Madhavrao (Shama), who was puzzled by this apparent partiality, as described in the text.