bump order is solely at the discretion of the gate agent (GA). and, the GA doesn't necessarily go by volunteer order if there are other circumstances. i was on a flight a while ago in which i was first to volunteer. after me, a family of three volunteered.

as it happened, the GA needed three volunteers and chose to skp me (i was platinum, the family had no status) so that the family didn't have to break up or so that she didn't have to completely skip the fAAmily (she had two other volunteers after the family so she could have skipped the family....she just chose not to skip them).

so, status and when you volunteered are considered but nothing is in stone. the GAA decides by AAny wAAy they see fit.