When you look at a label, say a low carb bar for example, it tells you how many carbs there are, how much fiber and how much sugar alcohols. Most bars do not have to put glycerine in their carb counts.
Any fiber carbs can definately be subtracted.
Some people have problems with sugar alchols and glycerine. Some people have no problems with them. The count depends on the person. I know that I should count all 25 or so of the carbs that a bar has.
Now talking about nuts, say macademia nuts. The label says (off the top of my head, not an exact count) 5 grams of carbs, 4 grams of fiber. You can subtract the fiber and have a net total of 1 gram of carb per 1 oz. serving.
Now, nuts and bars are not allowed on induction, but the same idea goes for vegetables, subtract the fiber.
A good tool you can use is
www.fitday.com it is a free site. It will not subtract your fiber for you, but at the box at the top it says how much fiber and you can subtract that yourself.
Good luck!
Beth