I've heard about a miracle with grapes. What exactly happened and how did it affect the devotee involved?

The miracle of the grapes centered on a skeptical visitor named Boss Dharamsee. Chapter 35 narrates that after Dharamsee mentally questioned Sai Baba for giving him grapes with seeds which he disliked, Baba gave him even more and commanded him to eat them. Upon obeying, Dharamsee was utterly amazed to find the grapes in his mouth were perfectly seedless. This experience was transformative; the text states, 'All his ego dropped away, and love for the saint was born.' He realized that Sai knew his innermost thoughts and had performed this miracle specifically for him, turning his doubt into firm determination and love for Sai.