As Bonnie wrote, it is safer and easier to just count total carbs. Atkins (with a T) does use net carbs, which is OK for real food vegetables, but the company extended that to fibers and sugar alcohols which some people do metabolize (subtracting sugar alcohols only works for a label to sell products). Since you don't have a book, this page is a good introduction to a general LC diet, https://www.dietdoctor.com/low-carb

Carbohydrates can be simple sugars or complex carbs like starches (in this case grains like oats) and fiber. Don't be confused by that sugar number on a label or nutrition tracker...to your body all carbs become sugar. So you add up all carbs for the day.

Are you in the US? Plan to use a nutrition tracker ? (You don't have to make LC complicated but you seem to be leaning that way) if so, a tracker like MyFitnessPal will give you a total carb count, and a separate fiber and sugar count for the day. You can custom the goals for a LC diet.