I liked that article
I figure a serving of sushi (at least the rolls) = one hand roll (which is usually cut into slices). A serving of ebi (shrimp) is two pieces.
And the calories can really vary - for example on California roll, depending on how much avocado is used, and whether the crab is a whole piece or was made into a 'crab salad' with mayo. Different places will use different amounts of rice (some use TOO much rice IMO). It's a tough call because sushi making is almost an art form, and every sushi chef is an individualist (at least at restaurants).