It's not just 8 homegrown.
It has to be 4 club trained, i.e. trained as a youngster with Man City, and 4 association trained, i.e. trained in England/Wales with any club as a youngster.
E.g., Hart, Milner, Clichy, Rodwell, Lescott (assuming they stay) will actually count as 4 association players + 1 'foreigner.
They only have Richards and Boyata as club trained.
Effectively, they need to find 4 players who played in Man City youth teams. They could have a squad of only 17 if they can't find any.