Best Practices

Normally customers have the same amount of licenses for the KACE SDA and the KACE SMA. And they follow the same licensing parameters.

For the KACE SDA Licensing , you can delete devices to free some seats, IF those devices you are deleting are already retired. (not being used within your organization anymore).

But at this point there is no DRM in place to control this, because you are free to delete as many Devices\Nodes as you want to free up some space.

But, this is from the End User License Agreement:

"(b) Excess Use. If an Audit indicates that Customer has engaged in Overuse, then Customer will be invoiced for all Overuse quantities at Provider's then current list price plus any applicable Overuse fees, which may include but are not limited to, interest on past due amounts and prior Maintenance Service fees. If the Overuse is more than five percent (5%) of the License Entitlements, then Customer shall reimburse Provider for Provider's cost of performing the Audit."

See:
https://support.quest.com/kace-systems-deployment-appliance/kb/186215/what-happens-if-the-k2000-appliance-licensed-seat-count-is-reached-or-exceeded-

this means that you can only deploy 500 different devices.
You can delete already deployed machines but this simply means that you cannot use use automated deployments and other features with it which is needed to mass deployment etc
The easier way would be buying the needed licenses.