That, and the temperature of the egg itself. Did it come from the refrigerator or is it at room temperature? Furthermore, not every egg has the same size or weight.
the temperature has been addressed in that article.
True but I am European and therefore, as mentioned in the article, often store my eggs at room temperature. The hardness of a cooked egg is a function of the size and/or weight of the egg, the cooking time and the temperature of the egg.