Sometimes, as in this label, the serving size is by weight. If you don't have a scale handy, pay special attention to the number of servings in the package.
When we are counting grams of carbohydrate, it's important to look out for "rounding error." For example, if a label says that 1 tablespoon of a food has one gram of carbohydrate, that could be anything from .51 grams to 1.49 grams. That’s not a big deal if you are eating one serving. But there are 16 tablespoons in a cup, so the error could be as much as 8 grams in either direction if you are using that much in a recipe.
A common example of this issue is heavy cream. One tablespoon of heavy cream has slightly less than half a gram of carbohydrate, which labeling regulations say is "zero." This has led some low-carb dieters to believe that they can use several tablespoons at a time. But these "zero carbs" can add up pretty fast.