I am not quite sure if I got your calculations right - are you saying that the consumed amount was sufficient for a very rough average of 793.3 fuel loads per day for September 1940 for example?
Now the calculation doesn't account for non-operational flights - this was looked into earlier, at around post no 87. It was found that three s-e Sqns that were looked at flew about 230 hours of training/non-operational flights in a single first week of August 1940:
54 sqn for example:
http://www.oldrafrecords.com/records/511/5110313.jpg
32 Squadron flew 60 and-a-half non-operational hours in the first week of August 1940, all of which were transfers to and from their forward base.
43 Squadron flew approximately 10 non-operational hours in the first week of August 1940, namely one transfer of six aircraft and their return and another transfer of seven aircraft, and three night practise flights.
54 Squadron flew approximately 159 non-operational hours
This works out as a rough avarage of 76 non-operational flight per Sqn per week, or about 300 hours a month per Squadron.