The first thing we have to know is that logistical growth is the per capita growth rate of a population that gets smaller and smaller as the size of the population approaches a maximum number of people. In the case of the zombie apocalypse, the dead would not count and the maximum population number would be the population of the U.S is 325,000,000.
For x = 0, they found 100 open graves so with this information we can find b
Then the growth equation will remain