[Ifeffit] How to evaluate the fitted result by LCF?

Dear, I want to consult how to evaluate the fitted result by LCF. R-factor within what range is reasonable and allowable? Attached are the fitted results, athena-SSRF.prj extention and .gif picture.Why there is still a large deviation for sample K (excluded FeSeO3 from this sample)? Thanks a lot! Best wishes Mingliang