Understand how promotion priority influences how promotions are evaluated.
The priority assigned to a promotion influences how promotions are evaluated where promotions with a higher priority take precedence over lower priority promotions.
The ability to prioritize promotions gives business users control over the promotion evaluation. The default promotion evaluation rules that the Commerce Engine uses to evaluate promotions can become complex when dealing with multiple qualifying promotions of different types. You can use promotion prioritizing to override some of these rules.
All new promotions default to the same priority value, including promotions provided out of the box. The system defined default priority value is 100, but your system administrator might have configured a different value for your Sitecore Experience Commerce solution.
When you assign promotion priority, keep in mind that the lower the promotion priority value, the higher priority a promotion is given when evaluated. For example, a promotion with a priority set to 25 takes precedence over a promotion with a priority value set to 100.