My understanding is that the 20 gm is a general guideline for the maximum amount of carbs to eat during induction, though some people can handle more, and some can't handle that many. I wouldn't worry about not eating enough carbs. It's difficult not to eat 20 gms a day. Most protein has some carbs, and you're bound to have to compromise occasionally on a sauce or something, if you're at someone's house, so you really don't need to make a concerted effort to eat enough carbs. You're better off eating less and then not stressing out if you're not perfect one day.