Well i think thats an indication of return -Looks like a overnight stopper with a FULL CSA flight number -NOT codeshare range these are four figure numbers
OK3--- , OK4---, OK5--- for Sky team partners AirFrance/KLM/Alitalia/Delta/Korean and Aeroflot plus a few others mainly Russian regionals Finnair and Malev !
The code share would surely be a reference to Skyteam partner Aeroflot .
Note the new Aeroflot web site also shows the codeshare via Prague and it one of a very few codeshare destinations advertised within Europe by Aeroflot.
I think we need to await a confirmation from CSA in the coming weeks.