Determines which billable numbers or delivery data (impressions, clicks, and so on) will be used for billing purposes.
||Charge based on the quantity of impressions, clicks, or days booked, regardless of what actually delivered.|
||Charge based on what actually delivered, as counted by Ad Manager.|
||Charge based on what actually delivered, as counted by the third party ads server.|
||The value returned if the actual value is not exposed by the requested API version.|