When Pre Day 1 is enabled in instance and also "Use the same User ID for Pre-day 1 User and the Employee" option is enabled in Provisioning, Same Pre Day 1 User ID being used when Candidate is Hired.
But Some Customer need to update as per EC Format
Successfactors Onboarding 1.0
Pre Day 1 user ID is taken from Bizx Company Settings and Logo Settings.
If you need to Update/Change the Pre Day 1 User ID to different Format, then navigate to below format.
Admin Center-> Company Settings and Logo Settings
Next Person Id Assigned-> Change the Number here
Pre Day 1, User ID, EC , KBA , LOD-SF-OBD-CHK , SuccessFactors Onboarding Check Tool , How To