The example is countries with Muslim populations. Wikipedia is (currently) telling me that India has more Muslims than Pakistan (179 vs 178 million) but if I follow the source quoted by Wiki I get to the Pew Forum which gives the figures as 178m v 177m in favour of Pakistan.
It's the Pew Forum's research and not anyone can edit it. So I trust this over Wikipedia. Perhaps an Indian Muslim perhaps changed the figure on Wiki so that his country has more muslims than Pakistan.
As it happens, the answer to the question I'm writing is Indonesia, but I thought I'd make a note here as it would be an otherwise-hard-to-spot mistake on Wikipedia and Wikipedia must be stuffed full of these types of tiny innacuracies that can derail a quiz question from its holy target of THE TRUTH!