Seagate has used an odd encoded value for this for years. You're attempting to read a raw value, which is meant for Seagate's internal tools. This is all documented.

smartctl knows how to parse it, it just never does by default (a long-standing bug that isn't high priority enough to fix).

Do `smartctl -a -v 1,raw48:54 /dev/xxx`, or `-v 7,raw48:54` for raw seek.

However, these values have never been useful to diagnose a drive as failing before data corruption appears (and it gets kicked of a raid), in my experience.