If it’s a U.K. book, the carbs should just be the total carbs (what you’re calling gross, I think). Do note that that cookbook is from a commercial company
not Diabetes U.K. (this site) which is a registered charity.
The official Diabetes U.K. shop is here:
https://shop.diabetes.org.uk/
.
The ‘org.uk’ differentiates this site and marks it as a charity, I believe.