Here how you can go about getting that information.
Create a dynamic watchlist with source MSSQL of the ePO backend. Then in the query section of the watchlist write a query to pull the repected information. Then create a Dashboard to present that data in a graph using the wachtlist as the source.
So i presume the firewall between the SIEM and the ePO DB needs to be established first before any query can work. Correct me if im wrong