The forecast is clear in Google Ad Manager

If you’re a publisher who sells advertising space directly to advertisers, you might have experienced times when you’ve been unsure about how much inventory is available for you to sell...

Google Ad Manager can help you learn what you have available to sell by forecasting your future inventory and subtracting off what you’ve already sold.

To learn more about forecasting in Ad Manager, visit the Ad Manager Help Center.

[Via Google Adsense Blog]