Under the drop-down menu, you can specify the range of your search: (A) in the VTC Institutional Repository, or (B) across all repositories using Digital Commons.
The default advanced search is set to "All Fields," which will query all the criteria used in a simple search (ie.. You may refine results using the drop-down menus provided, and use the +/- buttons to include additional criteria.
Notes:
The details search tips (http://repository.vtc.edu.hk/help-search.html)