The total amount of grants under §§ 42.1-48 and 42.1-49 shall not exceed the amount expended, exclusive of state and federal aid, by the political subdivision or subdivisions operating the library. If the state appropriations provided for grants under §§ 42.1-48 and 42.1-49 are not sufficient to meet approved applications, the Library Board shall prorate the available funds in such manner that each application shall receive its proportionate share of each type of grant. Applications must be received prior to June one of each calendar year.