Person DFF - Can a DFF be a multiple selection choice for the employee?

Content

We are creating a custom ethnicity self-ID list for the employee to complete - similar to the US ethnicity codes, but includes a few other codes that we prefer to track.  Thus, we created a custom list.  But in DFF, I am finding that they are not multiple selection choices, like that are in a extensible.  Did I select the attributes correctly or is there a recommended setup to allow an employee to select multiple options of a DFF?