After the board of supervisors adopts and files the resolution, the county is no longer eligible to receive any apportionment and the district agricultural association which thereby becomes eligible to receive an apportionment shall, for the purpose of determining its maximum base of apportionment, be entitled to receive credit for the fairs which were previously held by the county. They shall be considered as fairs which were held by the association in calculating the maximum apportionment base for the association.