For any fiscal year in which each Center described in subsection (a) receives a grant award of not less than $500,000 under subsection (a) (adjusted in accordance with subsection (b)), after making the grant awards, the Secretary may make grants under section 15061(a) of this title for activities described in section 15063(a) of this title to additional Centers, or additional grants to Centers, for States or populations that are unserved or underserved by Centers due to such factors as—