306.4. The sum representing the difference, for a given fiscal year, between the amount mentioned in the certificate contemplated in section 306.1 and the actual expenditures of the city of Montréal, is, as the case may be,(1) paid by the Community to the city of Montréal, within thirty days of receipt by the treasurer of the Community of a certificate of the director of finance of the city attesting the difference;
(2) reimbursed by the city of Montréal to the Community at the time of the sending of the certificate.