Most SMART attributes work like this: If it has a threshold and the value falls below that threshold, it (usually) causes the drive to mark this attribute as failed. It will stay that way for the rest of the drive's life.
In your case, there were a lot of errors reading (raw) data at some point in the past - within the 688 hours of the drive being powered on. How many errors there were is very difficult to tell, but honestly it doesn't really matter. I'd keep a close eye on the SMART values and if they worsen, I'd replace the drive, maybe RMA it if possible. And always make backups of your data - and verify them since non-working backups are like no backups at all.
Regards
Dalai
