The conclusion of “An Astrologer's Day” comes when the astrologer returns home to his wife and, after a quiet supper, explains to her in a few brief sentences the meaning of his meeting with the customer at the vendors' market. Up until the conclusion, the reader really has no idea of what the astrologer knows or doesn't know or, more importantly, of why he had to run away from his village under cover of dark in his youth. Plus, we have no idea how that event might relate to story or to the customer.
The conclusion explains that the customer is the reason for the astrologer's flight from home because he is the man the astrologer stabbed, as he believed, to death:
"[You] were pushed into a well nearby in a field. You were left for dead."
From this revelation we understand two other things about the astrologer. Not only was he protecting his own life by telling the customer that his attacker had died in "a far-off town," (1) he is also giving the customer the satisfaction of hearing that his attacker has met an end that might be considered just punishment for his deed, that of being "crushed by a lorry."
In addition, (2) he is exposing the truth about himself that all these years he has been trying to atone for his evil action by doing good to as many as he can by being a good astrologer who listens, understands and gives "good advises.” Therefore, the conclusion, the scene between astrologer and wife--to whom he has been so good that she has no thought he could have done evil--explains why he had to leave his village; how he knew the customer's life; why he kept trying to back out of the challenge; and how he knew what to say about the customer's assailant. It also gives insight into what kind of man the astrologer really is, and what his present motive in life has been: to atone: "I thought I had the blood of a man on my hands all these years."