There is no such thing as a negative carb. Probably the manufacturer already subtracted fiber from the carb count it listed — a more accurate label might say 9 grams carbs, 5 grams fiber for a total of 4 net carbs.

According to the Atkins Carb Counter, 1 whole artichoke has 13.4 carbs and 6.5 fiber. 1 marinated artichoke heart has 1 gram carbs and 0 fiber. http://atkins.com/global/carb-count...?cat=condiments