[John Vasco]

Marius,

One thing to bear in mind is that overclaiming occurred on all sides during the war, whether innocently or otherwise. Check out 74 Squadron's claims for 11th August 1940, or ZG 26 claims for 18th August 1940, or 242 Squadron during their 'Big Wing' operations towards the end of the Battle of Britain. All of these were way off the scale.

I would suggest that is what you are seeing for 18.12.1939 along the lines of what Chris Goss has suggested and stated in the previous post to this one.