Looks like each row corresponds to a different policy number. If you add the policy number also in the outer query you will see this:
CLIENT_NUMBER = 1027
AND M.POLICY_DATE_TIME = (
M.POLICY_NUMBER = M3.POLICY_NUMBER
POLICY_DATE_TIME DESCOne other thing to keep in mind is that if there is more than one row in the table for the same policy number with the same policy_date_time, you would get all those rows if that policy_date_time happened to be the MAX for that policy number.