I believe that Chainat had been rendered hors de combat on 7 September 1916 and that Guynemer's 8 February 1917 victory was his alone. "Over The Front" shows Chainat with only a single victory shared with Guynemer - an LVG two-seater on 22 June 1916.
I've tried to match Guynemer's claim with a German loss (as per
Casualties of the German Air Service) but haven't found a fit.
Graeme