This gauge, accumulated since the last reboot, reports the number of embryonic application-layer connections -- ones where the signaling channel has been established but the associated data channel is still awaiting setup. An admin cares about this because protocols like SIP or FTP open a control channel first and a data channel afterward, and a backlog here can indicate an application-layer inspection or NAT problem preventing the data channel from completing. For example, a growing number of embryonic connections for a VoIP deployment would suggest calls are getting signaled but their media streams are failing to establish through the firewall.