The majority of BIAB styles only have a/b sections. Anything past that (c/d, etc) are called Multistyles. These can be found in the StylePicker under Multistyles. The style name is typically followed by a plus '+' sign.

Every style has an a/b part. The 'b' is usually busier than 'a'. A multistyle has the a/b as well as definitions for additional styles for c/d, e/f, etc. These can be any other BIAB style and are defined when creating or editing a style. This is found in the StyleMaker.

Hope this helps