For purposes of computing or recomputing an annuity to a child under section 4046(c) or (d) of this title or section 4049(c) or (d) of this title, the items $900, $1,080, $2,700, and $3,240 appearing in
section 4046(c) of this title shall be increased by the total percentage increases by which corresponding amounts are being increased under
section 8340 of title 5 on the date the annuity of the child becomes effective.