how to prepare Excel file with custom field - dependent dropdown.

i'm creating new custom field - dependent dropdown - in my test case template.  I define value in parent and child (multiple value).  I don't know how to Excel file to serve import Test Case.  In field mapping step, i found parent value but no value appears in child.  

Below was my Dependent Dropdown which defined Field name as 'Feature', I had one column in Excel file

when import Test Case, need to complete details field mapping for this custom field (as image below).  

Need to confirm that what header name should I put in Excel for 'Child'.  Now I put like 'Function Option', 'Option', etc. but no value appeared in that dropdown list.