Sorry for the possible confusion, from the information I suspect your drive may be not so bad - but I'm afraid not perfect.
Generally the drive seems not working correctly, could not properly record possible errors and changes.
This is relatively rare, but happens, with some Seagate drives, caused by a firmware bug of some specific hard disks.
It is caused by an underflow condition: the drive previously encounter some minor problem(s) and when it tried to fix that, it decreased the error-counter twice (first to zero and then to -1 which lead to underflow to negative numbers in the internal error-counter of the hard disk drive).
Yes, generally there are reallocated sectors and also communication problems (at least according the text description).
Cables, connections are frequent causes of such issues, when the error counters may become damaged / corrupted.
Sometimes power source (accidental reset, shut down, sudden disconnect may be in the background.
Then the result may be exactly what you see: some of the attributes turn to really weird values.
Of course you can very easily fix the issue: as the test confirmed that currently the status is stable, you can remove the appropriate reported errors from the text description and restore the health of the hard disk the following way:
Please open the S.M.A.R.T. page of the hard disk and locate the attribute "197 Current pending sector count" where the Data field shows FFFD
Click on the "0" in the Offset column in this line and specify -65533 in the small window opened. Repeat the above for "198 Off-Line Uncorrectable sector count" attribute also.
( This procedure illustrated at https://www.hdsentinel.com/faq_repair_hard_disk_drive.php )
Soon these kind of issues will be longer reported in the text description and the health of the drive increases too.
Then only possible change, modification will be reported in both the text description and the health %.
However, as the drive has other issues (reallocated sectors) I'd be very careful about it. Yes, intensive testing is a good way to verify the status, confirm if the drive is stable at the moment, but I'd use only with caution and with constant monitoring and backup upon any, even minor change.
If possible, I'd suggest to please use Report -> Send test report to developer option, then I can check the complete hard disk status and may advise on the actual situation. The best would be if you can send developer report now (for reference) and maybe later upon any possible change. This way it is possible to compare and verify what happened, how the status changed.