Stefan,
Quote from Pg.106, "Black Fokker Leader":
"in any event, on the fine summer day of 25 June 1918, I brought my new Fokker D.VII back to our airfield(then at Lomme, at the western edge of Lille)"
Degelow then goes on to describe his victory over Lt. Jones-Lloyd of 54 Squadron in a Sopwith camel later that same day, the event you refer to. The way I read the passage it appears that Degelow got the first D.VII assigned to Jasta 40.
Cheers,
Lance