Please forgive my ignorance...we are lowly silvers and don't often get upgrades.

My son (CO Silver) is flying EWR-ATL this afternoon, on an X-fare. When I checked him in online yesterday, the system asked if he wanted to be upgraded. (Duh!) However, when I printed his boarding pass, it said he was added to the upgrade list, and it looks like he's number 1.

There are 2 seats available in first-class, so what are they holding them for?