DV stands for Dichiarazione di valore (*Declaration of Values,) which affirms your high school graduation has the same values as the Italian HS graduates.
DV certificate is issued after the formal "Pre-Enrollment" at your Italian Consulates General, where your "HS diploma" is issued and governed, NOT where you Reside (or Resided.)
Depending on the Italian consulates with appropriate jurisdiction of your HS qualifications, you may be required to submit "additional documents" such as SAT/AP score reports (*this is additional country-specific regulation and may differ from one country to another.)
Please contact us for more details.