Starting with the release of Strategy ONE (March 2024), dossiers are also known as dashboards.
Any contact that is linked to an enabled Strategy user will use a Strategy Distribution Services license. Each individual recipient of a report or dossier delivered by Distribution Services requires a Named User license whether that recipient is a user (with a login in the metadata) or a contact.
You can check the total number of contacts defined in the system through Strategy Developer> Administration > Delivery Managers > Contacts:

KB37681