The 'Mean time to remediate' is the average time taken to resolve security breaches from their discovery to their full remediation. This metric provides insight into how well the incident response plan is working and how quickly the organization can recover from security incidents. It is a critical KPI reflecting the effectiveness of the incident response team in dealing with threats. The other options are related to different aspects of incident response and reporting, but they do not specifically address the time efficiency of resolving the remediation process of security incidents.