International dollars are normalized to USD, so there’s no conversion necessary. The figure he quotes of 63 min per dollar converts to $8343/year. However, his original paper states that he created this measure by inverting income, so the number 8343 is his starting point.
The closest guess I have is that is derived from the poverty line for a family of four, $32150 (which divided by four is $8037).
If that is the case, what he is really doing is comparing poverty line definitions between countries.
So it's how much you earn per day divided by 24, or maybe by yearly earnings and hours per year
Think of it this way, its like difference between median and average income. Larger inequality, larger the gap between median and average.