If you want to list events that occurred in the last day, you need to add tblNtlog.TimeGenerated to your report and filter this expression. At the moment, you are
NOT listing events that occurred in the last day. You filtered the tblAssets.Lastseen column, which stores an asset's scan date, not the date/time an event was generated.
You can also use the MAX function to list the most recent instance of the event for each machine: http://technet.microsoft.com/en-us/library/ms187751.aspx