Within Surveys Satisfaction reports, a user can select to benchmark their scores against another period of time or a group of properties (if they fall within a corporate account).
When you select to include a benchmark, you will notice a "Delta" column will appear.
This "Delta" metric provides a percentage change calculation between the "total" column and the "benchmark" column.
Here's the formula used to calculate the delta:
["total" - "benchmark"]/["benchmark"] * 100