This sort of utilitarian "unit of suffering" metric has never made much sense to me. 1B people die in a given decade, each perceives or experiences some amount of suffering, so we have say 2B units of suffering, 2 units per person on average.
Is anything better or worse if 2B people die instead of 1B with the same aggregate amount of suffering? Average suffering reduced by half! What about 100,000 people instead of 1B? Those people presumably die horrific, painful, suffering deaths but now there a lot more people alive. Is that better or worse?
Classical Utilitarianism (Bentham, Mill) is about maximizing overall well-being (or happiness), not just minimizing suffering as a number. It's not just math with units, it's about the quality and context of experiences too.
There's also average utilitarianism which says: maximize the average happiness per person.
Is anything better or worse if 2B people die instead of 1B with the same aggregate amount of suffering? Average suffering reduced by half! What about 100,000 people instead of 1B? Those people presumably die horrific, painful, suffering deaths but now there a lot more people alive. Is that better or worse?