The recommended level for someone without diabetes is 90gm so, in a sense, anything below this helps and for diabetics, the lower the better. Another factor is how complex the carbs are and how much the food is processed. For example, pearl barley is high in carbs but because it is harder to digest, it has a very low GI. Barley flakes on the other hand, are easily digested and have a GI similar that that of white bread. Then there is your own personal metabolism, every person is different. Thus, the best way is to test, before and after (2hrs) meals and find out what works for you.
As an example, I have 1/3rd cup of oats as porridge for breakfast. Although fairly high in carbs, the portion is small and the oats take time to digest. I am under 7.8 after 2 hours. Lunch I usually do carb free, slices of meat, cheese or fish with salad veg and a mug of a warm broth . Evenings I'll include some carbs, something like 50gm brown rice, 3 small new potatoes boiled (not flourery) or pumperknickel. It probably amounts to 40gm carbs but, it is a sustainable diet. I have tried zero carbs and I did lose weight but had to stop after a couple of weeks. I just didn't feel well. Just test, eat and test again and experiment to find out what works for you.