Hi,
You will need to edit the View directly in SQL, I don't think the Lansweeper editor is capable, if you create a dummy report in the Lansweeper editor with the default SQL  and name it eg "chart: Test report"  , select "Save and Run" and the report will be displayed, take note of the ID eg -"web50rep56fgdgddggdgddd", Open the SQL Server Manger and browse to the Lansweeper Database and Views and locate the ID, edit the query and enter your SQL something like:
SELECT        OS, COUNT(AssetID) AS Count
FROM            dbo.web50rep56fgdgddggdgddd
WHERE        OS like 'Win 10%'
GROUP BY OS 
Save the Query and re-run the report in Lansweeper and the Query should work ?