What cookie does "Prevent Repeated Display'" use to determine if an intercept has been seen?

The cookie uses the domain or subdomain in which the user has visited. So, you will want to specify whether you want to prevent repeated displays for your entire site (dogtreats.com) or a specific subdomain of your site (giveme.dogtreats.com). If you prevent for the entire site, it won't matter what subdomain the user is visiting, they shouldn't see the Intercept. If you do just the subdomain, the user may see the Intercept when visiting a different subdomain of your page.