It is estimated that between 223 and 273 inhabitants of Lone Pine survived the earthquake.

The passage shows that there was "an estimated 250–300 inhabitants of Lone Pine" and that "27 are known to have perished". If we subtract 27 from 250, you get 223, and if we subtract 27 from 300, we get 273. Therefore, it can be estimated that the number of inhabitants that survived the earthquake is between 223 and 273.