Patrick, that 5% value was established empirically and given the number of possible combinations (the size of the radius and the offset of its center...
They don’t kill off everyone just say anywhere from 60-96% of population....
Consult the history section of your local library for previous examples...
I got excited when this guy started to explain what systemic racism is... but then he had to go back to studies in 2003 and 2014 to provide evidence....