This is the sequence number for this LSP. Because a higher sequence number always wins when two versions of the same LSP conflict, this is the field an admin compares across two databases, or before and after a topology change, to confirm which copy of a given LSP is actually the most current accepted version, rather than assuming the most recently received copy is automatically newest. For example, seeing this LSP's sequence number lower than what is shown for the same LSP ID on a neighboring router indicates this router's copy is stale and due to be overwritten as soon as the newer version propagates to it.