Imo, the exhaust wouldn't have a prism like effect that would cause a double-image like that. At least, I don't recall ever seeing such an effect.
The picture can still be genuine though, albeit with the number photo-shopped.
I don't think what we are seeing is a "double image".
Of the serial number "2016" that is distorted, I think the 1 and the 6 are distorted the most, however the 6 is half covered up by the J-10's engine nozzle, so the 1 is seen from the photographer's point of view through the camera with distortion with the most effect... and that distortion makes the "1" seem like half of a "0"... due to a combination of the engine's exhaust distortion, the possible heat of the day, as well as the distance of the subject from the camera.
I think distortion is a perfectly reasonable explanation. More importantly, there is no reason for the photographer to have bothered with PSing that particular number in such a specific way, especially when the rest of the photographs in his set are all untouched -- it makes no psychological sense for the photographer to to so.
I think all the pictures are genuine and the "double image" we see is merely a result of distortion, rather than the photographer PSing it for some strange unexplainable reason.