MULTI PLAYERS button extracts the statistics of all the CLIENTS from the "dcs.log" file  contained in the folder
c:/users/your user/saved games/instance of the DCS dedicated server used/Logs

SINGLE PLAYER button extracts the statistics of the PLAYER from the "debrief.log" file contained in the folder
c:/users/your user/saved games/DCS (or DCS.Openbeta)/Logs

It needs Microsoft Excel.