passengers are given their number to board the plane based on the order the check-in. normally, check-in starts at the 24 hour mark and creates what amounts to a virtual line. it's not always convenient to get in the virtual line right at the 24 hour mark, so early bird check-in is offered where the airlines computer gets in the line for you before the main queue opens at the 24 hour mark. the early check-in is also a virtual line in order based on when you bought your place in line..early buy before later.
when you obtain your boarding pass, even if you wait until you get to the airport, will reflect your standing in the early virtual line with no additional action by you beyond buying the early bird check-in. relax and have fun!