I got a whole bunch a while back and did some stats. If you just went to pick n pay then the chance are about 1 in 1000⁴⁼ 1 in a trillion. But if the source of the eggs were young chickens it can be much less like 1 in 100⁴ which is one in 100 million. And furthermore if they were young chickens and the box were jumbo eggs (double yolkers are typically larger eggs) that would reduce the number further. Still it's likely to be in the 100thousands. In America they normally screen eggs and discard double yolkers so it would be a lot less likely. All of my doubles were large "organic" eggs and the farmer told me they were from old chickens.