This feature allows you target up to 4 subdirectories per domain. Domain targeting will serve on all pages that fall into the string of subdirectories. For example, if you target https://www.nytimes.com/section/world/africa, your ads will serve in the World/Africa section, as well as any other section that sit below the Africa section.
Enter each Domain on an individual line in the ‘Custom Audience’ text box. This Audience has a limit of 50,000 Domains per list.