What's the story behind Appasaheb's promise to give ten rupees and why did he feel indebted?

The story, detailed in Chapter 33, explains that Appasaheb's family had previously given only one rupee to a Fakir, who was implied to be Sai. Appasaheb felt this amount was insufficient and made a personal resolution, stating, "Had I been there, I would have given ten times more." He thus gave his word that he would give ten rupees. This created a sense of unresolved debt because the promise was unfulfilled. The scripture questions how he could be debt-free without keeping his word, especially since this Fakir was not an ordinary beggar but someone testing his devotion.