The map shows the earnings of the poorest tenth of the population living in each territory. Japan is disproportionately large because Japan is the territory where the poorest have the highest average incomes. The larger the territory appears relative to its population, the better off its poor are in a global context.
India is large because a tenth of the population (105 million) earning a little each, earn a lot together.
In territories with the lowest per person earnings amongst the poorest tenth, measured in purchasing power, the poor earn less than 1% of the earnings of the richest groups of poor people.