A lot of people will use the net carbs on veggies and fruits because the fiber cannot be digested so it does not contribute to your carbs that are absorbed by the body.

As an example - take the avocado that you are eating:
100g gives you 9g of carbs and 7g of fiber, so the NET (actually absorbed/digested) is only 2 grams.

Another example - celery:
100g gives you 3g of carbs and 1.6g of fiber, so the net is only 1.4g of carbs.

To make this easier to see in my food diary, I eliminated the sugar column and replaced it with fiber - now the carbs and fiber show up next to each other and I can easily subtract the fiber from the carbs to get the net carbs that I am eating.