These kinds of graphs are usually used to represent how many individuals does a species have in a particular space distribution, for example, a forest, which can vary throughout time due to multiple factors, such as the food availability, other's population size, such as those of the depredators, and the partner, and resting space availability. What we can see in the signaled area with the X letter, since the curve is above the line that usually represents a limit in which the population is greater in number, is the overpopulation of the species.