The portion of the total amount available for allotment for any particular fiscal year under paragraph (1) which is not allotted to States for that year by reason of paragraph (3) (plus the amount of any reductions made at the beginning of such year in the allotments of States for prior fiscal years under paragraph (3)) shall be reallocated in such manner as the Commissioner of Social Security may determine to be appropriate to States which need, and will use, additional assistance in providing services to severely handicapped individuals in that particular year under their approved plans. Any amount reallocated to a State under this paragraph for use in a particular fiscal year shall be treated for purposes of this section as increasing such State’s allotment for that year by an equivalent amount.