Before the beginning of the budget year, the head of each office, department, or agency shall submit to the mayor, when required by him, a work program for the year, which shall show the requested allotments of the appropriations for such office, department, or agency by quarterly (three-month) periods, for the entire budget year. The mayor shall review the requested allotments in the light of the work program of the office, department, or agency concerned and may revise such allotments before approving the same. An approved allotment may be revised during the budget year by the mayor after consultation with the director or head of the office, department, or agency concerned. At the end of the fiscal year the sum of the four quarterly allotments made by the mayor shall not be greater than one hundred per cent nor less than ninety per cent of the total appropriation as made by the board of aldermen, unless unusual circumstances warrant otherwise. The term appropriation as here used shall include any supplemental, deficiency, or emergency appropriations and any transfers of funds authorized by state law or by this Charter. (Acts 1951, ch. 539, § 96)