There is a listing of sites for wpb standalone in its cpanel plugin. You can only see there how many sites have been created with wpb on that particular cpanel server. Could you add somewhere the total number of sites created with wpb standalone server. This could be added to for example to the License Management page.
Problem is that, when you have many servers it is hard to track how many sites have altogether been created.
Problem is that, when you have many servers it is hard to track how many sites have altogether been created.