How did Sai Baba demonstrate to Cholkar that he was aware of his personal struggles and devotion?

Sai Baba provided a stunning demonstration of his omniscience to Cholkar. Chapter 15 recounts that after Cholkar had fulfilled his vow to distribute sugar, he was a guest at Jog's place. As they were about to leave, Baba specifically instructed Jog to give Cholkar "cups of tea, well-filled with sugar." This was deeply meaningful because Cholkar had secretly given up sugar for a long period while he was unable to afford the trip to Shirdi. Baba did not even drink tea himself, so the comment was clearly for Cholkar's benefit. Baba later confirmed this, stating, "The state of your mind at the time of the vow, and the penance of the long delay— Though you kept these secret, all of it is known to me."