Modelling strength degradation (Strength loss)

Hello

In order to model the strength loss as a function of ductility in Ruaumoko one should define the "ILOS" parameter (e.g., see appendix A). If ILOS=1 then the strength loss in each direction is a function of the ductility in that direction and if ILOS=3 then the strength loss in each direction is a function of maximum ductility.
I do not quite understand what is the difference between these two cases. Dose the maximum ductility refers to the maximum positive and negative ductilities (i.e., absolute ductility)?
Anyway I have found that using LOS=1 and 3 can significantly change the results and I think using ILOS=1 some times lead to problematic results (probably due to bugs in Ruaumoko). It is appreciated if some have information in this regard to discuss this. Thanks.