Why did Sai Baba treat the two gentlemen from Goa differently regarding their money offerings?

In a curious incident detailed in Chapter 36, two gentlemen from Goa came for Sai Baba's darshan. Although they arrived together, Baba's interaction with them regarding Dakshina was markedly different. He specifically asked one man for fifteen rupees, which the man gave with joy. However, when the second man voluntarily offered thirty-five rupees, Baba immediately rejected it. This apparent partiality surprised everyone present, including Madhavrao (Shama). When questioned, Baba began to explain that he himself takes nothing from anyone. He stated, "Mother Masjid demands what is owed, and the giver becomes free from debt." This suggests the transaction was not a simple offering but the settlement of a past karmic debt.