The ‘People’ metric is specific to Cross-Device analytics virtual report suites. It represents the sum of individuals who are identified in the report, plus the number of devices that are not identified as belonging to a person.
If a visitor is identified mid-visit, that visitor can count as 2 People (1 unidentified person and 1 identified person). Replay mitigates this double counting depending on the reporting window, replay frequency, and success rate. See Unique devices for more information.