Update cpp/includes/defines.h

Co-authored-by: Alex H. Room <69592136+alexhroom@users.noreply.github.com>

Author: StephenNneji

cpp/includes/defines.h

@@ -501,6 +501,8 @@ struct NameStore {
 const std::string docsChecks = R"(The Python binding for the C++ checks struct which contains 
 flags indicating which parameters should be fitted in the project.
 
+For each attribute, if index ``i`` is non-zero, then parameter ``i`` in that attribute is fitted, e.g. if ``Checks.scalefactors = [0.0, 1.0, 1.0]``, then the second and third scalefactors are fitted and the first is not.
+
 Parameters
 ----------
 params : np.ndarray[np.float]