This is the MPLS label value this router uses when sending traffic toward the peer for this pseudowire, i.e. the label the remote end advertised to this router via LDP, again with -1 indicating no label has been received/allocated. Comparing this against the inbound label field on the same pseudowire, and against what the peer reports as its own inbound label, is a standard way to verify LDP label binding has completed correctly in both directions. A -1 here while the inbound label shows a valid value would point specifically to a one-directional signaling problem, perhaps because the peer hasn't yet advertised its label back to this router.