A goal forecast is an estimate of how likely a campaign is to meet its selected goal, such as a specific number of clicks or impressions.
These forecasts are a way to confirm whether there will be enough clicks or impressions available for a campaign, and they can help you plan for shortages that may be likely to occur. Forecasts can help you optimize campaigns and prevent overbooking or underselling.
When you run a forecast, AdMob runs an instant simulation of the ad server to determine how competing campaigns will be delivered across the forecasted inventory. An initial forecast can be run during campaign creation, and additional forecasts can be run by editing a campaign.