The ad valorem fees prescribed in section three of this article are for the entire fiscal year: Provided, That when application for a proportional registration is made between August 1, and the thirty-first day of August, inclusive, in any fiscal year, the fee for registration is eleven-twelfths of the yearly fee; when application for the registration is made between September 1, and September 30, inclusive, in any fiscal year, the fee for registration is ten-twelfths of the yearly fee; when application for the registration is made between October 1, and the thirty-first day of October, inclusive, in any fiscal year, the fee for registration is nine-twelfths of the yearly fee; when application for the registration is made between November 1, and November 30, inclusive, in any fiscal year, the fee for registration is eight-twelfths of the yearly fee; when application for registration is made between December 1, and December 31, inclusive, in any fiscal year, the fee for registration is seven-twelfths of the yearly fee; when application for registration is made between January 1, and the thirty-first day of January, inclusive, in any fiscal year, the fee for registration is one half of the yearly fee; when application for registration is made between February 1 and the last day of February, inclusive, in any fiscal year, the fee for registration is five-twelfths of the yearly fee; when application for registration is made between March 1 and the thirty-first day of March, inclusive, in any fiscal year, the fee for registration is one-third of the yearly fee; when application for registration is made between April 1 and April 30, inclusive, in any fiscal year, the fee for registration is one-fourth of the yearly fee; when application for registration is made between May 1 and the thirty-first day of May, inclusive, in any fiscal year, the fee for registration is two-twelfths of the yearly fee; and when application for registration is made between June 1 and June 30, inclusive, in any fiscal year, the fee for registration is one-twelfth of the yearly fee.