There isn't any, really. Acesulfame potassium is Ace-K, an artificial sweetener. In this case maltodextrin is a filler; as all sugars are carbs and your product has 3.9g of carbs then there could only be 3.9g of sugar (that is if there was any at all). While artificial sweeteners are not sugar they do contain carbohydrates, just not many of them.
If you're avoiding sugar because of a specific dietary requirement (in your case, acne) you can use this product.