I know what you mean. I thought at least I could have some sugarless gum...wrong. Not only does it have 1 carb per piece but it uses aspartame and I am trying to cut all of that out of my diet.
Some dieters subtract the sugar alcohols from the total carb counts while others avoid sugar alcohols because they cause them to stall. I would, to quote my great aunt - "everything in moderation." If a piece of gum helps you avoid a piece of cake - it's still a win-win situation. If you eat the entire pack of gum instead of something very low carb and fillng - maybe not a good choice. If it makes u crave carbs - avoid it. I say sugar alcohols are "frankenfoods" and for the most part I avoid them, but as before, one piece of gum is better than 1 piece of cake.
I would guess that either someone made a math error, or a typographical one (maybe the mint weighs 5g instead of .5).
I've found both kinds of errors before. I'll often use my digital scale just to solve the mystery (even if it's a difference that really doesn't matter. I tend to be bugged by "puzzles").