How does Damu Anna's story serve as an example of the power of one-pointed devotion mentioned in the text?

Chapter 25 explicitly introduces the story of Damu Anna to illustrate a core principle: when a devotee establishes one-pointed faith, Sai Baba wards off their misfortunes and grants their desires. Damu Anna, a devoted but childless man, exemplifies this. His unwavering devotion is highlighted by his long-standing vow to provide a flag for the Ram Navami festival. As a direct result of his faith and Sai's blessings, he, who had two wives but no children, was blessed with sons. His experience is presented as proof that the 'Guru-Mother is an Ocean of Mercy' and that suffering is removed for those who worship with such singular focus.