This is the numeric position of a given stage within the ordered sequence of steps that make up the chassis-profile-association FSM, per its definition as the FsmStage order property. Because UCS runs FSM stages strictly in order, comparing this value against the known total stage count for the workflow tells an admin how far through chassis association a specific chassis has progressed. A stage reporting order 3 out of a workflow known to have 7 stages tells you that chassis's association is roughly in the first half of the process, not finished.