How i filter last 6 hours performane if i dont have a time column. if i run the system at 10.00PM then it will fetch the system time that is 10.00Pm - 6Hrs so the report display the value between 4.00PM to 10 PM so on at 11PM the value display from 5.00PM to 11PM.
Some thoughts on high level.
You may want to use the current_date and current_time to construct your start time and end time, so you can use them in a filter.
[Reoprt Time] BETWEEN StartTime AND EndTime
I am not an expert so others might be able to help . . .