If there are multiple managers in a position, how do serial approvals choose the manager

Summary:

If you have approvals (for personal contributions/absence/etc.) configured to be serial approvals, and you have a situation where the HCM Position hierarchy is being used, how will the approval rule decide which manager to select if there are multiple incumbents in the manager position?

e.g. Abbey Employee submits a personal contribution request, Barry Manager and Chris Manager are both sitting in the manager position for Abbey's position. On Abbey's assignment we see Chris as the line manager, but in the approval transaction it's gone to Barry.

How has BPM Worklist decided this? Does it base a decision on routing the approval to Barry if Chris has more approvals in flight? Or does it choose alphabetically by name?