This Counter64 totals the Phase-1 security association delete requests received across all currently and previously active Phase-1 control tunnels, per its description - distinct from the Phase-2 delete requests tracked elsewhere, this is specifically about a peer telling this device to tear down the IKE control tunnel itself, not just a data SA underneath it. A rising rate here reflects peers actively closing their IKE tunnels with this device, which is normal during scheduled maintenance windows but abnormal if it happens unexpectedly during production hours. An admin seeing a burst of these requests outside a maintenance window would investigate what caused multiple peers to simultaneously tear down their control tunnels.