Disk Utility Erase function doesn

HI all,

I had a problem with my SSD on my Mac Book Pro ( early 2015 ) that it got corrupted, and I was unable to disk repair it.

So I created a boot partition on my external HD and tried to erase my SSD so I would be able to reinstall OS X on it.

But I'm having a problem that using Disk Utility it isn't erasing it, and it isn't allowing me to install OS X on it because it doesn't have enough free space.

I've tried to erase it, delete the partition, recreate it, erase it again, and again, but every time I'm left with something like this, with around 200GB of used space reported to the system, but with no files at all when I go through finder.

There isn't other volumes on it

How can I fix this

TIA