Grocery store soup bar serving size

I recently bought and ate some ready to eat soup from my local grocery store which was nice enough to have the nutritional information by the crock of hot soup. However, today after reheating and thinking about the numbers, I am starting to question the serving size. The information says 1 serving is 227g = 1/2 cup. I portioned the soup by volume into my bowl, forgetting the info has a weight as well, and didn't think to weigh it until after reheating. After reheating my 3 servings (1/2 cup each) of soup, I weighed it and got about 345g (used a same type bowl for tare, could be off a bit). There is absolutely no way I lost almost half of the weight of the soup during 3 minutes of microwaving at 70% power. So now I am questioning what exactly is a serving.
According to the label, one serving has 310 calories, 23g of fat, 15g carbs and 11g protein (it's creamy chicken wild rice) so what do you think? Should it really be 1 cup for a serving or is the weight completely off or between their heating and my heating did I really lose that much weight from water evaporation? Or do you think it started as a concentrate and somehow that accounts for the much higher density of a serving.
I would normally just go with the higher amount but in this case it's almost 500 calories in question. I don't want to eat that much extra but I also don't want to be in that much of an extra deficit when my deficit is already at 1.5 pound per week. If no one has a better idea, I may just split the difference.