If 1/2 cup of ice cream is 20 grams total carbs, how many carb grams in 1 tsp. of ice cream?

Dreyers Fat Free No Sugar Added Ice-Cream [with Splenda] reads 20g total carbs, 6g dietary fiber, 4g sugars, 3g sugar alcohol. So if I were to have a nibble, maybe 1, 2 or 3 teaspoons, of this ice-cream, how many net grams of carbs would I be taking in for each teaspoon? And how did you figure out your answer? I would really appreciate knowing. :-) Thanks!