Retrieve the report totals of the most recent campaign sent to a list. This is the v3 equivalent of calling the v1 campaign_report_totals action with only a listid.

"Last" keeps the v1 definition: the highest id among the campaigns sent to the list, not the latest send date. A list with no sent campaign is a 404.

The response is the same shape as Retrieve a campaign report totals, and the same date window rules apply: startDate and endDate must be sent together.