What was the specific miracle that Sai Baba performed with the grapes, and how was it confirmed?

The miracle of the grapes is a well-known story from Chapter 35. Devotees had offered grapes that contained seeds. When Baba offered these to Boss Dharamsee, Dharamsee was reluctant because he disliked seeded grapes. He ate some and pocketed the seeds. When he held more grapes in his hand, troubled, Baba instructed him, 'Throw them in and eat.' Upon putting them in his mouth, Dharamsee was amazed to find they were all seedless. The miracle was further confirmed when he asked another devotee, Babasaheb Tarkhad, 'How were your grapes?' Tarkhad replied that his grapes did have seeds. This confirmation, as described in Chapter 35, made Dharamsee 'extremely surprised in his heart,' solidifying his belief in Baba's divine power to alter reality based on a devotee's inner thoughts.