LOL! Sanford’s silly “Mendel’s Accountant” program is a joke, an exercise in self-delusion. It was purposely written so no matter what initial values were input the population would “degrade” and die within a thousand years. It has absolutely zero connection to biological reality.
Just for fun some people put the starting population of 8 from Noah’s Ark in and humans died out in less that 100 years. Oops!
Oops!