One thing that is especially important to notice when adding custom segments and not just demographics to your kits is that reach will be reported as coverage. The reason for this is that the data regarding custom segments is based on unverified 3rd party sources, whereas regular demographic segments can be verified by cross-referencing data from national statistical banks. For instance, we know from Statistics Denmark that the 18-24-year-olds in Denmark represent around 9% of the online population, while the proportion of the online population that is in the market for buying a new car is an estimate based solely on survey answers.
To make a clear distinction between validation of the audience based on statistical banks data and the ones based on unverified 3rd party data, we distinguish between reach and coverage.
If you have questions or need help to handle this setup please feel free to reach out to our Client Service teams on firstname.lastname@example.org