Not sure what your query was as that was not provided and often times you could just assign the report to existing device group of let's say SERVERS ..
Having said that if all you need are your OS drives then you will need a query to just return that drive letter. Then assign report to proper device group.
As far as the erroneous processor core count.... not sure I follow... are you saying we show too many cores? I am sure these are virtual and you must understand how VMWare handles shared cores.. you may need to run a wmi script and output results and then collect using regular expression if you are trying to match the assigned processor count. Go back thru the hardware inventory of a sample server and ensure you are pulling the right field in the report.
There must have been a hang up some place. I recreated the sub report and added the query back in and it is showing the correct information now.