When such traveling public show or carnival has completed its performance and is about to depart from the City, the Mayor shall ascertain all costs incurred by the City as a result of the traveling public show or carnival appearing within the City and shall so advise the auditor of the costs so incurred, who shall then deduct from the aforesaid five hundred dollars ($500.00) deposit the cost so incurred, and who shall then refund to the person who made the original deposit, the balance of the deposit remaining.