The dusk speck is a slight irritation. Hearing about somone being tortured is a bigger irritation. Also, pain depends on greatly on concentration. Something that hurts "twice as much" is actually much worse: lets say it is a hundred times worse. Offcourse this levels off (it is a curve) at some point, but in this case that is not problem as we can say that the torture is very close to the physical max and the speck's are very close to the physical minimum pain. The difference between the Speck and the torture is immense. Differense in time = 1.5 M. Difference in hurting 2 M. So we can have a huge number (like 2 Million to the power of 24 Mi to the power of 1.5 Mi). This number is going to be huge. Even if this does not add up to our number of specks one can see that one can define perimeters to make either side the better choice. In the end it is just a moral question.