This is the source location, for example Check Point's update servers or the local SmartCenter, from which the last Anti-Virus signature update was retrieved. An admin checks this when diagnosing a stalled update, to confirm the gateway is even reaching the expected source, since a gateway pointed at an unreachable or wrong update mirror will keep checking without ever successfully updating. For example, this showing an internal SmartCenter address rather than Check Point's public update service would explain why signatures lag behind gateways that update directly from the internet.