How is percentage data applied to the population in the US Cities Database?

In the US Cities Database, demographic percentages, including age, correspond to population_proper, which represents the population residing within the city limits. As an example, let's consider Los Angeles, where the percentage of individuals aged over 60 is 9.8%. Therefore, the number of people in their 60s would amount to 9.8% of the total population_proper of 3,902,440.

Here is the link to the US Cities Database: