What happened on the specific day that Sai Baba had predicted Tatya would pass away, and how was it seen as an 'exchange'?

On the day Sai Baba had foretold Tatya's death, a remarkable event unfolded. Chapter 42 narrates that as the Vijayadashami of Shaka year 1840 arrived, Tatyaba was severely ill with a fever, his pulse weakened, and relatives began to grieve. At the same time, Baba's own physical suffering increased. Then, a "wonder happened" where Tatya's life-danger passed, and he recovered. At that very moment, Sai Baba himself left his body. People interpreted this as a profound exchange, believing Baba averted Tatya's death by substituting his own physical form, a testament to his mysterious ways and deep compassion for his devotees.