From the LibCentral DASHBOARD, you can get a list of all the OWNED titles (one line per unique title).  In contrast, the Expenditure Report includes a separate line for every transaction (STL, credit, purchase) for each book.  These two reports include very different information and aren't easily compared - in particular, do not expect the number of lines in the Expenditure Report to be the same as the number of owned titles.
 

From LibCentral DASHBOARD, click “OWNED” titles, click “Export Results”, choose CSV:
 

From LibCentral “Reports” tab, “Expenditure Report”, do a blank search (no special settings)

From LibCentral “Reports” tab, “Expenditure Report”, “View Expenditure Summary