On a 10 MC muscle loss is not an issue. I've done more that a dozen 40 dayers and never had any muscle loss. Just remain acitve and get some exercise and you be just fine.
While grade B is preferable because it's got more minerals it's not the end of the world if you do it with A. The syrup is just for nutritional support and on a "minimal" 10 dayer it's no big deal.