I'm unfamiliar with the product, but it sounds like the sugar substitute is still carby, although when it comes to sweeteners, not all of them affect our bloods. I'm afrain you're going to have to look at the probably minute print on the pack (or ask Dr Google) for the sweetener name, then ask Dr Google again if it is likely to raise your bloods.
If the sweetener is sorbitol, or any of the names it goes by, just be careful not to have too many or you may find yourself dsitracted by a fascination for sanitary ware. (i.e. - spend an extraordinary amount of time in the loo!).