I ran chkdsk /r last night on my primary HDD and it reported and allegedly "recovered" (I think) 4 bad sectors. What does that mean and is there any way I can tell exactly what it did and did not do?

So I'm working on the HDD of a laptop of a friend. I'm not sure wtf was done to this machine, but there has been a bit of reallocation due to bad sectors. Unfortunately, chkdsk seems to be running ...