That's why some applications refer to the next move as 'A'. Applications show variations as either siblings or children. That is, by selecting a variation, you step forward in the tree. The differences between this two styles may cause confusion when the variations are accompanied by comments. See variation 'B' instead.
Most people prefer the sibling style as it seems more natural.
They even imitate the sibling style in children-style applications. This is bad style . Furthermore those files cannot be converted to other fileformats easily. Board markup SGF provides a wide selection of board markup. Almost every markup you see in magazines or books is available in SGF too.