i followed the tutorials
but for some reasons, on the lofted surface,
some part offsetting and filleting worked, but others.
is it because of lofted surface that i drew at the beginning ?
(I changed each control point a little bit to make the surface narrow to wide)
or.. any other solutions?
-Hana
Parametrics 
silly question, i figured that out with the amount of offset ..
Yep! Offset amount and/or input surface[s] size.