I think it's more likely they meant a millionth or a billionth the second time - it's much more common to talk about the size of galaxies in terms of their rela

I think it's more likely they meant a millionth or a billionth the second time - it's much more common to talk about the size of galaxies in terms of their relative radius than talking about their volume, which you can't directly measure and that's much harder to compute.