An insertion order or line item's budget is the target amount of money that Display & Video 360 will attempt to spend buying impressions, or the number of impressions that Display & Video 360 will attempt to buy. An order or line item's pacing determines how quickly Display & Video 360 will try to spend the order's or line item's budget.
Monetary budgets use the total cost based on the partner revenue model, not just the media cost. They lead to slightly more volatility than impression-based budgets.
How does an insertion order's budget affect its line items?
An insertion order's budget and pacing settings have the effect of capping the budget and pacing settings for the individual line items contained within the order. However, the sum of the budgets of the line items in an insertion order don't need to be equal to (or less than) the insertion order's budget.
For example, if an insertion order has a budget of $100,000, but the line items within the order have a combined budget of $105,000, the line items contained within the order will only be able to spend a maximum combined total of $100,000. Similarly, if an order had a daily pacing goal of $3000, all of the line items contained within the order won't be able to spend more than $3000 per day (combined), regardless of their individual daily pacing goals.
Similarly, pacing at both the order and line item levels sets a cap on how much of its budget the order or line item can spend each day. Display & Video 360 respects the lowest cap, whether it's the line item's cap or the cap for the order, and limits delivery accordingly.
If the cap is reached for a given line item, it will stop serving for that day, even if the order's cap hasn't been reached. Likewise, if the order reaches its daily cap, its line items will stop serving for the day.