Drobo

How to delete Time Machine Backup 5D3

I have been using a 5D3 with my iMac. I created a 2TB partition to hold my Time Machine backup. I’m in the process of moving to a new iMac. And deleted the contents of this partition (I have another Time Machine backup) in order to restart a Time Machine backup with the new computer. However, after deleting, the folder still appears near full. Even after restarting. Is this normal?

Is there any need to reformat a partition? Or is this even possible?

Appreciate any suggestions.
Steve