To be clear -- time of check in is the last tiebreaker, after status and the fare class purchased. So, if you were on a relatively expensive ticket, you would have remained ahead of the other silvers even if you had checked in a little later. (Although, I do echo the advice for a Silver to check in at T-24 except when trying to avoid getting the PNR split, as encampbe alluded to).

It's also possible that the other people on the list were non-revs, who would also have appeared after you regardless of check-in time.