Hello,
The Luftwaffe summary aircraft losses is a Luftwaffe document that has been put online by Andreas Brekken and co (thanks to you).
URL is
http://www.ahs.no/ref_db/lw_summ_los...iew.asp?PAGE=1
This is the public access giving access to the summary of losses. All JG units are covered and some extra units, but most KG and TG units have not been entered in the database. The source covers 1944 and is especially useful for this year.
As for 27 August 1943, I would say we are missing a I./JG 26 loss:
I./J.G.26: 2 destroyed by gunfire from enemy aircraft during operational flight, observed by enemy (reported on 31/08/1943)
I./J.G.26: 1 destroyed by gunfire from enemy aircraft during operational flight, observed by enemy (reported on 11/09/1943)
Next step would be to check GQM loss lists for 31 August and 11 September 1943. Either the above is true and a third loss was added on 11 September, or it is a typo, or a correction that has been wrongly entered as an addition.