The amount of the annuity of a spouse of an individual provided under subsection (a) of this section shall be increased by an amount equal to 45 per centum of that portion of the individual’s annuity as is computed under subsection (b) of section
231b of this title: Provided, however, That if the spouse is entitled to an annuity amount provided by subsection (e)(1) or (e)(2) of this section, the amount of such spouse’s annuity provided by the preceding provisions of this subsection shall be reduced by the amount by which the amount computed in accordance with the provisions of clause (C) of subsection (e)(1) or (e)(2) of this section was increased by the Social Security Amendments of 1965, 1967, and 1969, disregarding