The fuel table compares plog burn and actual burn for each calendar month and is influenced very heavily by the routes flown. Some routes consistently give savings of 500-1000kg, others you will be lucky to save 100kg. In general those at the bottom will include people who have had missed approaches, diversions etc and also people who have only flown a few sectors and thus not had the advantage of a spread of routes and averaging. So basically it isn't really that statistically interesting since it compares people with 4hrs and 115hrs.....