It doesn't specifically say a carb limit/target. If you follow the meal plans in the book then you don't need to track carbs. If you design your own meal plan then my advice is to be very aware of the frequency of certain foods in those original meal plans.
I get flamed for this in the Facebook group I'm in, (not on here because we're all nice people) - no food is allowed 'freely'- as in, everything has a cap on the amount you can eat if you want the big weightlosses. For example: Fruit- is allowed, in small quantities. Check the amount of fruit portions in a week's menu plan, it's about 1 piece every 4 meals, and some of those are things like pomegranate seeds in a salad, not apples, pears etc. Fruit is never used as a snack. So even 'allowed' fruit is limited. This applies to dairy, grains, nuts etc. as well, and even to some meats (particularly processed/cured meats). We obviously are naturally capped by the calorie limit as well.
The 50g carb limit was already in place in these sorts of forums when I joined in thread 2. It can be helpful, to a point, especially if you want something but don't want to break your plan (ie. Thinking like slimming world syns!). Personally I find it gives me too much leeway to have things that aren't really on plan, or too much of things, and actually the big weight loss for me comes when I don't have certain foods even within a carb limit. As with all these things, the quality of calories you eat makes a difference- so 50g in the form of leafy veg, dairy, fibre, nuts is going to be better for you than 50g carbs in the form of hobnobs (not that you would eat hobnobs!)
I really would make the meal plan in the book your bible. It's been formulated by nutritionists at great expense, and the balance is accurate. If they use bulgar wheat twice in a week, then use that as your guide. I find on these FB groups people see 'porridge' or 'quinoa' on the menu and think it's ok every day; you can eat it, but it will impede your weight loss and you will he sacrificing other nutrients to have it within your calorie count.