You can now see the FP% along with the total emails processed, and total threats detected in the overview section of Impersonation Protection.

False positives is the percentage of messages marked as threats that were actually good emails. An asterisks here means the percentage is less than 0.001%. You can hover over this number to see the actual percentage.

Campus: https://campus.barracuda.com/product/sentinel/article/preview/98212871