When running an Advertising campaign there are multiple factors that affect your spend, such as audience size, competition, day parting and bidding type, just to name a few. When running trying to stick to a pre-set budget the fluctuation on a daily basis can make your monthly (or other period) spend higher or lower than anticipated.
Often there are learnings in the initial part of the period, and then you will want to tighten things up at the end to ensure that you hit your target. To facilitate this Budgets utilize a Starting and Ending Threshold to determine the status of a Budget at any given point in time.
The Examples graph below show a Budget that is set with the default thresholds in both the Series and Cumulative graph types.
How to read MTD Avg.
MTD Avg (Month to Date Average) Is a metric to help you understand how much on average you have spent per day for the current calendar month. Most advertisers want an even spread of spend throughout the month to ensure that ads are always visible. So keeping this value around your target is important to ensure that you will spend the correct amount. If it's above then you are likely to overspend by the end of the month and vice versa when it's low.