@YLIL If you open the computer record for the already erased Macs you want to "release" the Jamf Pro license for and then select the General category under Inventory tab you'll see an Edit button in the upper-right section of the General information. Click the Edit button, then un-check the "Allow Jamf Pro to perform management tasks" checkbox that will be shown, then click Save. That will change the computer to un-managed in your Jamf Pro inventory.
If you don't care if the computer record remains in Jamf Pro, you could just click the Delete button visible in the lower-right of the window when viewing a computer record in Jamf Pro.
