[Ifeffit] the meaing of "beta=125.264" in path interpretation

Dear, Firstly, i'm very grateful for the useful responses from Bruce Ravel and Matt Newville on my previous question. Now, I have another question about path. The screenshot below is the interpretation of a path in α-Fe. I was wondering what does "beta" means. Is that scattering angle? I tentatively construct a triangle according to the rleg values, and find that the three angles are consistent with the beta values. What does this mean? I searched the Artemis user guild and the mailing list, but could not find the answers. Do you have any ideas? Thanks in advance Qiang Chang Institute of Coal Chemistry, CAS Leyuan South II Street 1, Yanqi Development Zone Huairou District, Beijing, POB. 101407 P.R. China