What are Summary Variables in CPQ and how are they used in Price Rules?

Summary Variables (SBQQ__SummaryVariable__c) perform aggregate calculations across all quote lines or a filtered subset, returning a single value that can be used in Price Conditions or Price Actions. Configuration:

1. Source: The quote line field to aggregate (e.g., Net Total, Quantity, Custom Field).
2. Type: The aggregation function — SUM, COUNT, MAX, MIN, or AVERAGE.
3. Filter Field / Value: Optionally restrict the aggregation to lines matching a condition (e.g., only lines where Product Family = "Hardware"). Use cases in Price Rules: (a) If the total quote value (SUM of Net Total) exceeds $500,000, apply an additional 5% quote-level discount — the Price Condition references the Summary Variable. (b) If the count of Professional Services lines is greater than 3, set a capped price on additional lines. (c) Percent of Total pricing on support products often uses a Summary Variable summing the platform product net totals. Summary Variables are evaluated during the CPQ calculator run and are always computed before Price Rule actions that reference them.