The same happened to me. I took lettuce salad with feta cheese (yuummm) and it counted zero carbs for the cheese (which actually says it has .7 gr, and accordingly to the hidden carbs calculator has only 0.65). But the vegetables was perfect, cucumbers 2 per 100 grams (discounting fiber) and so on.

Anyway, as this happens I decided to go by the book, so I counted 4 gr of carbs because I took 4 oz of cheese (well, half of the salad - 2 oz cheese - for the evening).

So, even if my fitday says I got only 12 as a total today (dinner included) I am counting it as 16 (giving some room just in case I forgot to count something).

I guess it will take us some time to learn about the carbs, in the mean time we will have to keep checking on the book, carbs counter of this website and the fitday.

Hope it gets easier later. Good luck