Depending on the information in the import file, some duplicates may be Format Conflicts on step 4 of the import.
Format Conflict indicates that the address does not match the format for what was chosen in step 1 of the import. For instance, if we chose United States as the country on step 1 and then tried to update an account marked as Canada with a Canadian address we would see this in Format Conflicts. We should choose to Ignore these lines and do a separate import for that country, or update those accounts manually. If we choose to update these accounts, they will be changed to United States.