Actually, the folks whose names currently appear on the list have checked in, and have requested an upgrade. The green check means they are confirmed for the upgrade, and included in the list of 28 booked.
There could be others on the upgrade list, above and below you, confirmed or not, but you don't see them on this list because they have not checked in yet.
There could also be crew confirmed in J and not included in the booked list. Sometimes you will see the list of checked in exceeds the list of booked.