How did Sai Baba demonstrate his ability to know the inner thoughts of his devotees during the incident with the grapes?

Chapter 35 provides a powerful example of Sai Baba's mind-reading capabilities. When Boss Dharamsee was given grapes with seeds, he thought to himself, 'If he is a saint, how does he not know That I do not like these grapes?' In response to this unspoken challenge, Baba gave him even more. Later, after experiencing the miracle of the seedless grapes, Dharamsee tested Baba again in his mind, thinking, 'If you are a saint, then the next ones will be given to Kaka.' Immediately, Baba gave the next handful of grapes to Kaka. This direct and immediate fulfillment of his unvoiced thoughts convinced Dharamsee of Sai Baba's extraordinary sainthood and omniscience.