If the sum appropriated by section three¹ amounts to less than thirty million dollars ($30,000,000) annually during the calendar years 1956 or 1957, 1958 or 1959, 1960, 1961, 1962, 1963, 1964 or 1965, there is appropriated for each of said years out of the Motor License Fund an amount equal to the difference between thirty million dollars ($30,000,000) and the lesser amount provided by section three, which sum shall be paid to the municipalities in accordance with the provisions of section four.²