The Calhoun County Commission may provide supplemental compensation to the members of the county board of equalization up to an amount to be set by the county commission so that the total compensation of the board members will not exceed seventy-five dollars ($75) for each day the members are engaged in the performance of the duties of the board. The supplemental compensation of the members of the county board of equalization shall be paid out of the general fund of the county upon warrant drawn on the county treasury.