Japanese codes (AIJ standard) steel structure design equation

Hello,

I am working on STAAD.Pro V8i and I can read in the help manual, for the Japanese codes 2005 steel design that
the equation for the Allowable bending moment stress correction factor C is written:

C=1.75 - 1.05 (M2/M1) + 0.3 (M2/M1)^2

I am using  a 2011 version of the "Design standard for steel structures - Based on Allowable Stress Concept - " standard book,
and in the book, the equation is written:

C=1.75 + 1.05 (M2/M1) + 0.3 (M2/M1)^2

I am a bit confused so I would like to ask if:

a- This is a typing mistake of the help manual,
b- This is how the software was coded,
c- The standard has changed and the software is using a new version of the equation,

or is there an other reason fo this discrepancy?

Thank you very much.