It takes about 25 hours for an egg to go through the hen’s internal egg factory. That egg can only be fertilized in the first few minutes of that journey. That means if a successful mating takes place on a Monday, Monday’s egg cannot be fertile. Tuesday’s egg may or may not be, depending in the time of the mating and when that egg started its journey. I would not count on it being fertile. Wednesday’s egg will almost certainly be fertile.
Note that is after a successful mating. A rooster does not always mate each hen every day. After a successful mating, the hen normally stays fertile for about two weeks. Some may go a bit shorter, many can go longer, but you can generally count on two weeks. So all he needs is to mate each hen once every two weeks to do his job. One reasonably active rooster should have no trouble keeping 14 hens fertile.
Like the others said there are factors that determine how soon that will be, but just follow Aart’s link and look for the bull’s eye. If most of the eggs you open have the bull’s eye, most of the eggs you don’t open will too.