Hi,
Realists take empirical science, both about observables and about unobservables, cognitive and truth like, and in contrary their anti-realists colleague limit the cognitive content of empirical science to observables domain.
This sentence needs some revision, as it is not clear. I've suggested some changes, but I may not have reflected your meaning correctly because I don't fully see it from the original.
Realists believe in empirical science, for use with both the observable and the unobservable, for both knowledge and truth alike. On the contrary, their anti-realist colleagues limit the cognitive content of empirical science to the observable domain.
Best wishes, Clive