Dear Steve,
I puzzled to about the way that is expressed! In the original article (which I cited) it says literally:
Low-GI diets reduced HbA1c by 0.43% points (CI 0.72–0.13) over and above that produced by high-GI diets.
So I don't think it is a typo in my article or in the original. But I do think that the reduction is about half a percentage point, as us laypeople understand it.
Best regards,
David