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.