slightly off topic: SMART error values for seagate drives

[Quartz]

Is anyone familiar with exactly how the raw_read_error_rate, 
reallocated_sector_count, seek_error_rate, hardware_crc_recovered, and 
udma_crc_error_count values work for seagate drives?

AFAIK at least some of these fields list the (average?) number of 
sectors between errors, and thus a higher raw value is better ...I 
think. I have several apparently healthy seagate drives with very high 
rrer/ser/her raw values that seem to support this.

I recently took an older disk out of storage, and as part of my system 
building procedure I always run a few tests over it before putting it 
back into service. Initially it also had high rrer/ser/her raw values. 
It failed a SMART extended test at about 40% remaining with a read 
failure, and the udma_crc_error_count jumped from 0 to 5. I know 
sometimes this can be just transient flakiness, so I just zeroed out the 
entire drive with dd to exercise all the sectors and force any 
remappings. Now, the reallocated_sector_count bumped up to 9, and the 
raw_read_error_rate and hardware_crc_recovered fields plummeted from the 
millions down to like 13 ...and have since slowly risen to the 40's.

I can't tell what's going on with SMART values anymore, every vendor 
does things differently and nothing's ever documented. Is having the 
reallocated sectors value go up still a bad thing, or did seagate change 
what this means? Why did the read error rate and crc recovered fields 
bottom out, but the seek error rate is still in the clouds? Is this 
drive failing, or fine, or what?