Some sugar alcohols are not digested and so can potentially be deducted from the carb count - I don't follow this personally and only deduct dietary fiber.
Regarding the Atkins bars, if you plan to use them on the Ideal Protein protocol, be VERY aware of the FAT content. Atkins does not restrict fat, while IP is a low fat diet on top of everything else. Most Atkins products are too high in fat for IP. Fat calories should be below 30% of the total calories per serving.