Web ADI upload to mass update email addresses assigned new employee number

We are on R12.1.3.

 

We had a request to do a bulk update of email address (per_all_people_f) for approximately 350 employees.   We created a new Web ADI Integrator that contained the following:

Header:  EFFECTIVE_DATE, DATETRACK_UPDATE_MODE

Lines:  LAST_NAME, PERSON_ID, OBJECT_VERSION_NUMBER, EMAIL_ADDRESS, Messages

 

The email addresses were updated; HOWEVER, we discovered that new employee numbers were assigned to these employees.   Their assignment record still shows the old employee number.     Our employee numbers are auto-generated.

 

Does anyone have any idea why/how the employee number would have been re-assigned?  

 

Melinda