STAAD.Pro: how to input Lb for AISC 360 steel beam design

Dear all,

I am modelling a simple roof steel frame and the steel beam design is not passing the design check for AIS-360 LRFD LBT

I have defined UNT and LY for the steel beam and it should meet the condition of Lp < Lb < Lr, however the design results shows the nominal flexural strength Mn is calculated for the case of Lb > Lr (F2-3)

I thought STAAD would consider UNT or LY  as Lb, but it didn't?

Could someone please help me to understand what I did wrong here~? Thanks.

Below please find the STD file:

steel roof.STD