The calculation of net carbs is only relevant to the US market as their total amount of carbs includes dietary fiber, too. That means that carbs in the US = carbs + fiber. 
To calculate net carbs, you subtract the fibers from the carbs > in the US carbs - fiber = net carbs.
In Europe however, the fiber is already subtracted from the total amount of carbs. So in European nutritional data, the total amount of carbs is the same as the total amount of net carbs. That means you do not see any settings/option to choose, as it is irrelevant. You are able to choose between carbs and net carbs in the keto Diets and Meal Plans available in the app:
- Ketogenic Strict
- Ketogenic Medium
- Ketogenic Easy
- Keto Burn
- Ketogenic Maintain
In order to choose net carbs, choose your preferred way when changing to the Diet/Meal Plan to one of the ketogenic ones. Or, please go to your Settings and then to the Nutrition Settings.
There you can choose between the two options and activate the requested one by ticking in the field. You will save your choice by leaving the page clicking on the arrow on top of the page.
Depending on what you choose you will either see carbs or net carbs in your diary.

Since we do not support sugar alcohol in our app our approach can differ a bit from other net carb calculators.
 In our app we calculate net carbs = total carbs minus fiber.
This is the net amount that will affect your blood sugar (such as sugar and starch) - the rest (fiber) are not broken down in into glucose (sugar), but instead goes down in your stomach to be food for the gut bacterias. 
Therefore if you have e.g. a total sum of carbs with 45 g and the fiber amount of it is 39 you will get 6 gram net carbs (45 gram total carb - 39 gram fiber).
The activation of net carbs is only relevant if you are using the app in English. For the rest of our markets the total amount of carbs = net carbs.

Avocado US:
Carbs: 8.5 g
Fiber: 6.7 g
Net carbs: 1.8 g
Avocado Europe:
Carbs: 1.7 g
Fiber: 4.8 g