Duplicate values show the values that appear at least twice: in
this case, the correct values will be found here. There are 8 duplicate
values.Let's check the rows with these values: right-click on duplicate count and select view rows:1) Clear the Limit Rows check box2 )Re-run the query3) Sort the duration column in ascending orderNow
you can see that 0, 6 and 12 values are only present a few times,
whereas 30, 60, 120, 180 and 300 are frequent. We can assume that these
5 numbers are valid duration values.