If you find yourself trapped in a caved-in mine for a few weeks, you might be happy to subsist on 400-900 calories per day. However, you are not going to be able to feed 4 people for six months on that kind of ration. This seller doesn't show the caloric value of the servings here on Amazon, and it's not easy to find even on their web site. That alone is troubling. When you do find it, you'll see that what they are counting as a "serving" consists of as little as 150 calories!
If you are stocking food for long term storage, be sure to pay close attention to caloric values, as well as nutritional components of what you're getting. A lot of food storage companies consider a serving to be much less than what you need to thrive, so don't confuse "serving" with "meal". Also, most of them load the meals with cheap carbs. Great for energy in the short term, but long term, you're going to need more protien than these meals offer. In addition to prepackaged meals, consider stocking up on freeze dried meats and vegetables that you can add to these noodle and rice based meals to boost protien and nutrition levels.
Bear in mind that although regular canned foods won't last as long as freeze dried or dehydrated, they don't need to be rehydrated, thus conserving precious water. Storing freeze dried vegetables in one container and water in another ends up using more space than if you had just bought canned food to begin with. Buy case lots when it's on sale and rotate it through your kitchen when the expiration dates are approaching. With canned foods, you don't even need to cook it (although of course it will taste better when heated).