As to why americans do things differently, I really don't know, but from a dietary point of view it makes sense to list fibre separately as we do 'here' (and the Eades and Atkins agree!) The only subset of carbohydrate on 'our' labels are sugars - which also makes sense as all sugars are carbs, but not all carbs are sugars ... yet (until you digest them).

As far as Fitday is concerned, that is an american site so the american rules apply (you subtract fibre). The same is true of a site like the USDA food comp site;

http://www.nal.usda.gov/fnic/foodcomp/search/

but if you use one of 'ours' eg. Foodstandards;

http://www.foodstandards.gov.au/npc/npc_calc.cfm

then the Australasian/European rule applies.

Cheers,

Malcolm