IDs are meant to be unique. Use a CSS class (and corresponding selector ".number") instead.
Once you have them all showing, i'm guessing they'll be showing up all at once. In order to fix that, you'll probably need to create a function that slides in the next number and sets a timeout to call itself again. Like,
function slideNext()
{
$(".number:first").each(function() {
$(this).slideDown("slow").removeClass("number");
window.setTimeout(slideNext, 1000);
});
}
$(document).ready(slideNext);
Note, this is not tested, and i am not by any means a jQuery guru.