Here are 2 different sources for computing eAG/ABG from A1C (and reverse computation checked on Accu Chek site):
So, for example, for A1C of 7 we get eAG/ABG of 154 by both these sources. This is the most popular and in vogue method of computation and not some obscure and not in vogue method.
Which is relating well if we do reverse calculation on:
Which for 154 will give A1C of 6.99 ~ 7.0
So, let's follow the standards rather than follow some obscure calculations/formulae to defend some wrong conversion numbers