In most recipes, one 'large' egg may be substituted for one 'extra large' egg, without any noticeable difference in the result. The same goes for 'medium' and 'jumbo' sizes.
The classification of an egg size as 'large' is based on a minimum weight of 24 ounces, while 'extra large' eggs have a minimum weight of 27 ounces. When a recipe calls for an egg without specifying the size, it typically refers to the 'large' size, which is equivalent to about three tablespoons.
Only in recipes where precise proportions are key (such as sponge or angel's food cakes) should minor variation in quantities be of concern.