How did Sai Baba prove to Cholkar that He was aware of his personal sacrifice regarding sugar?

Sai Baba demonstrated his omniscience in a subtle yet powerful moment. According to Chapter 15, after Cholkar had finally arrived in Shirdi, fulfilled his vow by distributing sugar, and was having a conversation as a guest of Jog, a pivotal event occurred. As Cholkar was about to leave, Baba instructed Jog, 'Give him cups of tea, well-filled with sugar.' This command left Cholkar amazed, bringing tears of joy to his eyes. The significance was that Baba did not drink tea, and more importantly, it was a direct reference to Cholkar's secret penance of avoiding sugar—even in his own tea—during the long delay in fulfilling his vow. This confirmed that Baba knew every detail of his unspoken devotion and hardship.