What is the deal with shiitake mushrooms?

According to Fitday, "normal" mushrooms (cooked, from fresh, fat added in cooking) have 8.03g of carbohydate and 3.42g of fibre per cup.

But Shiitake mushrooms (cooked, with salt) have 20.71g of carbohydrate and 3.05g of fibre per cup?

That's a huge difference! I had no idea! What's going on? Why is one mushroom so different to another?

I really blew it yesterday then, I had at least a cup of Shiitake mushrooms. I guess they will be firmly off the menu in future though.