; (ii) not more than 2 Federal renewable electricity credits for each megawatt hour of renewable electricity generated on Indian land; and (iii) not more than 2 Federal renewable electricity credits for each megawatt hour of renewable electricity generated by a brownfield site generation facility. (B) Adjustment Except as provided in subparagraph (C), not later than January 1, 2021, and not less frequently than every 4 years thereafter, the Commission shall review the effect of this paragraph on the aggregate quantity of renewable electricity produced under the standard and shall, as necessary and after providing 1 year of notice, reduce the number of Federal renewable electricity credits per megawatt hour issued under this paragraph for any given energy source or facility, but not below one, to ensure that the number is no higher than the Commission determines is necessary— (i) to incentivize incremental renewable energy generation on Indian land and brownfield sites