This is a free-text label an administrator can set on this endpoint for their own identification purposes. For this blade's physical port into the chassis backplane fabric, usrLbl is purely operator-supplied — UCS Manager never sets or interprets it — so its only value is whatever naming convention the local admin team decided to use, like a rack location or application owner tag. An admin might set this to something like 'DB-Cluster-Uplink-1' so the port is instantly recognizable in the UI without cross-referencing a spreadsheet.