What vow did Cholkar make to Sai Baba for his job exam, and how did Baba later prove He knew all the secret details?

Cholkar, facing financial instability, needed to pass an examination to make his job permanent. As recounted in Chapter 15, he made a firm vow to Sai Baba that if he passed, he would travel to Shirdi and distribute sugar candy (khadisakhar) in Baba's name. After passing, Cholkar was delayed in fulfilling this vow due to household expenses. As a personal penance for the delay, he secretly gave up sugar. When he finally reached Shirdi and fulfilled his vow, Baba demonstrated his omniscience by telling another devotee, Jog, to serve Cholkar "cups of tea, well-filled with sugar." This specific command astonished Cholkar, proving that Baba was aware of both the original sugar-related vow and the secret penance.