According to the preface, how does the creation and study of a Guru's biography serve both the author and the wider community of followers?

The preface explains that a Sadguru accepts service from devotees through books, one method being by having his biographies written by them. According to Chapter 0, by studying and performing Parayans of such a detailed poetic Guru biography, the writer performs a direct Guru service. Simultaneously, when other devotees in the community also study and perform these Parayans, the writer is credited with the merit of serving God in humanity (Jan-Janardan) and public service. This communal study allows the other devotees to also achieve the purpose of their lives, fostering a shared spiritual journey.