I bought used HD with ridiculous read/write stats once I looked at Seagate Tools' drive info. How could this happen?

I bought a couple of boring old Seagate 2 TB drives (7200 rpm) that the owner said were used in a NAS for a short period. Power-on hours are only ~300 (~12) and ~500. But Lifetime Bytes Read on both reports more than ~25 petabytes (PB), and Lifetime Written almost 1 petabyte.

I've having a hard time believing that much hard drive activity is even possible in ~12 days of power-on. (I mean, ok definitely not.) Is there something about being in a NAS that screws up these stats? I am worried that I've bought drives that have been thrashed to death and could die any time.

I only remembered that it was possible to retrieve disk information like this after I had purchased.

How concerned should I be whether these drives are going to be unreliable with minimal use (data or backup drives). Thanks for your advice!