This Gauge counts Far End Unavailable Seconds — actual outage time reported by the remote end via FEBE — accumulated at the Line layer during the current 15-minute interval. An admin cares because this represents real service-affecting downtime experienced by the far end due to what it receives from this device, directly relevant to an SLA conversation about the outbound direction of this link specifically. For example, a nonzero Far-End UAS count with zero near-end UAS confirms the outage was one-directional and traceable to this device's transmit side.