That is what I thought as well. I worked that out from the Collins carb thingy. It doesn't however say it is for 100g under the fast food. It just says portion is 30 cho.
If you look under potatoes though it says homemade fried 150g is 45 cho so that is why I decided 30 cho was for 100 g.
My little French carb book, (online here complete with pretty pictures of what portion sizes look like) http://www.medtronic-diabete.fr/tl_files/FR/PDF/brochure%20glucides.pdf gives 40g carbs for 100g of Frites. French potaotes have more carbs than British ones? !! I normally use this but I have to do a dual wave, or when on MDI give one small injection upfront and another later or I'll have a hypo within an hour of finishing eating (presumably because of the fat content)