Donation limit adjustment increases allowable deduction when specified donations push aggregate over threshold, capped by income percentage or fixed ceiling. Where the aggregate of deductible donations includes donations of the specified type and exceeds the prescribed basic limit, the basic limit is increased to cover that portion of such specified donations equal to the excess over the basic limit, subject to a cap that the raised limit shall not exceed ten percent of the assessee's gross total income as reduced or a fixed monetary ceiling, whichever is less.