Unless you specify, FitDay assumes cooking with some sort of fat for vegetables. If you just use the Search feature, that's what it gives you. If you use the Browse feature, you can select peas, cooked, fat not added in cooking (I assume; all the veggies I enter are this way but I hate peas so I've never tried it for those!) and it would probably be much closer to raw.
However, cooked food and raw food do take up different volumes, so this may also account for a slight to moderate difference, depending on the food.
And now that you don't have to be perfect, you can be good.