How many kids are you allowed??- foster/adopt

Hey I'm new (well new to posting-not to reading!) I'm dreaming of a VERY large family in the future :)!! That federal law about sibling groups is really interesting, thanks. Does it apply only to the children to be adopted, or to the kids already in the home? I.E. if you have say 8 kids in the home, but they were adopted as 4 sibling groups of 2, does that count as 4 children? Or is it just that any new sibling groups count as "1 child" in that respect?