Total Carbs include Sugars, Sugar Alcohols and Fibers
If a supposed sugar free item it should be void of actual sugars but will contain sugar alcohols or not if the sweetener is not an alcohol.
The alcohols all have a varying impact on the GI and I am sure there is a chart somewhere that lists these.
Fibers although they are a carbohydrate they do not impact the GI that much and for all intents and purpose can be removed from a carb count if counting carbs. In fact high fiber foods generally reduce the GL. For instance watermelon has a relatively high GI, but a low GL this is due to the fact that watermelon has a lot of fiber and a lot of ahhhh water.
GI= how fast the carbs convert
GL=how the whole food impacts serum sugars
So the lower the GL and or GI typically the better when on a low carb diet