The program's cost per mille benchmark refers to:

Cost per mille (CPM), or cost per thousand, is a standard metric in advertising that measures the cost an advertiser pays for one thousand views or impressions of an advertisement. It's a common way to price web ads and is used to compare the cost-effectiveness of different advertising channels. The percentage of potential customers who interacted with the content refers to an engagement rate, not CPM. The dollar amount spent per engagement is cost per engagement (CPE). The number of views, while related to impressions, is a raw count, not a cost benchmark.