Flat reports show data in a flat structure, that is, no group-by (each of the values is shown in a separate row). This report type is ideal for analyzing a large data sets (click id's, publisher id's etc ). It is the default report when choosing items that are unique (such as TID, IP, ClickID)"
To use the Flat Reports option, turn the switch on.
We strongly recommend to run this report on the background as it might take some time.