Total Carbs vs Net Carbs

Are you doing low carb or keto?

If not, its not anything you need to worry about and no wonder you are confused.

My understanding then, that for keto a lot of people use net carbs, that is total carbs less total fibre content. Fibre is indigestible therefore not included.

yes that's it.

http://www.ketogenic-diet-resource.com/counting-carbs.html

Net carbs are partially bogus, so best not to use them. The problem is they don't differentiate between soluble and non-soluble Fibers. Soluble fibers ARE digested, so you WOULD need to count them. Insoluble are not, so you do not need to count those.