Singular: You have selected %1$s attendee for %2$s. You can move it to a different ticket within the same event, or to a different event.You have selected %1$s attendee for %2$s. You can move it to a different ticket within the same event, or to a different event.
Plural: You have selected %1$s attendees for %2$s. You can move them to a different ticket within the same event, or to a different event.You have selected %1$s attendees for %2$s. You can move them to a different ticket within the same event, or to a different event.
This plural form is used for numbers like: 1, 21, 31