My fitness pal net carbs?

So this is my first week on keto and i’ve been using my fitness pal to track my macros but after days of not understanding why i couldn’t fit into my carbs when i was only eating meat, eggs, cheese and veggies i realized it actually shows total carbs so now i’m confused. I looked it up and apparently if i subtract fiber from my total carbs i’m left with net carbs? For example my total carbs for today were 49g, fiber 36g so are my net carbs 13g? Or is it wrong to calculate it this way? Seems a little too good to be true so i wanna make sure this is right 😅