Typically surveys are adjusted for sampling biases before reporting. That appears to be the case here. So there is usually some attempt to account for the biases in the sampled population.

The impulse to ask "what population was sampled?" is good but its not always a straight line from there to "these results directly reflect that sampling bias."

In fact, from the page you posted: "Data for the general U.S. population (including the High Net Worth oversample) were weighted to Census targets for education, age, gender, race/ethnicity, region and household income. A full methodology is available."

I would presume that the headline number attempts to account for sampling bias.