"I thought that to mean, what I have to do is half of a banana, 1/2 small sweet potato one slice of sgww grain bread etc. "
I didn't quite understand why you mentioned these foods, Of all the foods that I avoid you have just listed my top 3...... If you added to this pasta, rice and regular potato this would complete my list of foods not to eat.
Also one point to mention re portion control, I never now experience the burning hunger that had to be satisfied with carbs (bagels donuts etc) since I started to eat in this way. so the body does automatically limit the amount of food that is eaten when meals consist of fat protein and leafy greens.