Please solve this maths argument I am having on facebook?

According to Wikipedia, maginal utility is "the first unit of consumption of a good or service yields more utility than the second and subsequent units." I cant see how this applies in this situation. When the extra egg is added, that 4g fat is still there - it's not going to just disappear. The fat is a more tangible thing than, say, how useful a good or service is perceived to be.