a. In municipalities operating under a calendar fiscal year, immediately upon receipt of the director's certificate the county board shall fill out the table of aggregates required by R.S. 54:4-52 and shall determine the amount of "other local taxes" for the year based upon the certificate of the director. Upon completion, the county board shall transmit a copy of each municipality's table of aggregates to the director. If the local unit shall have adopted a budget for the calendar fiscal year and shall have transmitted a certified copy thereof to the county board on or before April 10, the board may substitute the adopted budget in the place of the amount certified by the director, but no such substitutions shall be made after May 1, unless otherwise approved by the director.