Reclaim space from External Hard Drive

[Wee Liang]

I am on macbook. I have been using a 4TB external hard drive to backup using time machine. My backups took 0.5TB. I have deleted ALL backups from my hard disk. It still show 3.5TB space left when I would expect the whole 4TB. Why is this so????

 

[Weaselboy]

Did you empty the trash with the drive still attached after deleting the backups?