Unfortunately Simeon doesn't provide any guidance in terms of a threashhold of acceptable limits in terms of natural sugar and starch (as you can see, berries even have a small amount of starch! It's next to impossible to avoid completely) I suspect that back in his day, nutritional data for most foods wasn't widely available, so he couldn't tell people to eat a set number of carbohydrates because they'd have no practical way of counting them. So just saying no sugar no starch, and avoid the most starchy/sugary foods such as pasta, pototoes, rice, sugar grains, corn, peas/legumes and very sweet fruit was the most practical guidance he could give.

I have approached P3 very methodically and try to keep my carb count as low as possible when faced with choices. I have done Atkins in the past, and I use his "induction" food list as a refence point, because everything in it is ok for P3-- free of sugar and starch. For Simeon's plan, I add a little more low-carb fruit (berries), higher amounts of vegetables, and some plain Greek yogurt.