Area and Subarea on change management

Hi Expert!

I have customize the area and subarea on the changemangament, We are able to see the data which are stored in area and subarea, The issue when area and subarea field is not populating its only populating subcategory. 

I am unable to add more value subcateogory with same name, For eg: Interface it throughs me error duplicate name,

I have attached screen shot with error message.

 

Customized field area and subarea on change management.docx