Removing Dell Latitude ST2 Tablet Admin Password

I have received a master unlock password from Dell for the tablet.

I access the screen by pressing volume down button immediately after pressing the power button.

Previously, I could not Unlock the Admin Password, but only received an "Invalid Password" error.  With the Dell master unlock code, I entered the code and deleted the Admin Password by pressing Enter instead of typing a new password.  It appeared to work.

 I still get an Enter Admin Password window when later trying to update bios with the Dell A09 bios update file.

I assume I'm screwing up somewhere.  This is the input screen.

How do I clear the Admin and System passwords completely from the tablet?