[Ifeffit] question about S02 (passive electron reduction factor)

Dear Ifeffit folks, This is Yu-Chuan. I am now trying to fit my sample, magnesium orthovanadate. I try to follow Bruce's Cu example and Scott's ZnO example steps and I found a problem come to my fitting. At the beginning of the fitting, the S02(amp) are far away from 0.9 (just about 0.3). It's much different than Bruce's and Scott's examples. For Cu and ZnO examples, the fitting results of amp are close to 0.9 at the beginning even if you set just four parameters (guess:amp, e0, delr, and ss). Also, John have said that the S02 value should be around 0.9. That's why I am wondering if there is anything wrong with my data processing? Does anyone happen to have this kind of problem? Thank you for your help. Good day Yu-Chuan