In general, +2 would mean that the flight arrives 2 days after departure. This is not uncommon especially when you're crossing the international date line where you lose a day whilst in flight. eg, flights from San Francisco to Australia always land "2 days" after they depart - despite only being a ~15 hour flight.
However, that itinerary does not cross the international date line, so the +2 is odd.
The flights that correspond to the times you've mentioned are AF1269 (MAN-CDG) and AF264 (CDG-ICN). Normally, there would be a ~4 hour gap between the first of those flights landing and the second departing, and you would arrive in ICN on the day after departure (ie, +1)
It is possible that you actually have booked flights that give a ~28 hour layover in Paris (which would result in a +2 day arrival), however in this case that does not appear to be possible as AF264 does not fly on the 3rd of October, and there are no other flights that arrive in Seoul at 7:10am.
Most likely wherever you are seeing the details showing as +2 is thus incorrect, and you actually arrive in Seoul on the Monday the 3rd of October. However I would be checking with the airline to make sure of that!