That seems pretty bad to me. It's showing around 250Gb of bad clusters, probably not accurate.
I'd suspect the drive may have failed mid-stream while running chkdisk. It's more common than you might think as chkdisk is really stressing on the drive.
I hope you have a backup of the data.
I'm just surprised, because I've been using computers since '94 and never had a failing drive in my life.
I have no backup, but I'd only be sad for a couple of days if I lose all my data on the drive, since half of it's is porn and the other half is TV series. But, the thing is, I installed some windows security update and restarted, then it suggested me to run chkdsk during boot(out of nowhere), but I was in a rush and since it's not the boot drive, I skipped it, thinking that I'd run chkdsk inside the OS. Then I opened a pdf file from the drive and then tried to go into a folder and it didn't let me, saying it was corrupted. So I tried to open every single directory, but everything was working fine, except for that one folder. So, I tried to open that folder again and the drive went nuts and told me to format it. So I scheduled a chkdsk on startup and restarted, and here I am.
The only question is, should I restart and see how it behaves in the OS, or should I wait at least for an another 24h to see if it's going to do something on it's own?
And is there a way to know, if it was my fault or windows' or just bad luck? Because besides me never facing sth like this before, this is an 8 month old drive(fairly new to me).