We have a Facebook ad running under a "post engagement" campaign and have set the "ad optimized for" option to "post engagement".
We get two options for "what you get charged for": impressions, and post engagement.
The bid shows as "X value" per post engagement.
How does Facebook charge for "impressions" (if we keep the default option selected to pay for impressions)? Wouldn't it only be valid to charge for "post engagement" given our ad optimization setting?