[Ifeffit] Linear combination fitting

Hi, I have a general basic question about linear combination fitting (LCF) with Athena. I have XANES spectra from two different mixtures. Both were mixed from two reference compounds in a 1:3 ratio. In one mixture the ratio is based on the weight of both reference compounds and in the other the ratio is based on the concentration of the element of interest (the concentrations in the reference compounds are not equal). If I am doing LCF on these spectra, which spectra would yield to the expected weighting parameters 0.25 and 0.75? What actually represent a normalized spectrum? Is a normalized spectrum a spectrum what one atom of interest would produce ? thanks a lot, jens