What is the amount claimed for this customer?
SELECT t1.amount_claimed FROM claim_headers AS t1 JOIN policies AS t2 ON t1.policy_id   =   t2.policy_id JOIN customers AS t3 ON t2.customer_id   =   t3.customer_id WHERE t1.amount_piad   =    ( SELECT min ( amount_piad )  FROM claim_headers ) 
amount claimed refers to t1.amount_claimed; this customer implies a specific customer_id needs to be identified or provided; amount paid is the least (minimum) refers to min(amount_paid);