Oracle Business Intelligence

Unexpected single default value selected within the list of values for a parameter
Oracle Business Intelligence 12.2.1.4.0
Hi,
I’m coding a BI Publisher report using a Data Model.
There is a parameter within the data model for employee number. Linked to this parameter is a list of values using a SQL script to find all eligible employee numbers.
This is the setup for the Employee Number parameter (no default value is specified):
...but when running the data model to return output, or the associated report, the Employee Number value 00000 is default selected within the list of values for that parameter:
I was expecting nothing to be selected - just a list of values to select if I want to.
Is this expected behaviour?
Does it happen because I have the "refresh other parameters on change" ticked? I've done this so the list of Employee Names will be refreshed to confirm the Employee Numbers selected are for the correct people (or someone can enter an Employee Name instead of an Employee Number if they wish).
Thanks,
Gavin