Audited IP addresses limit reached

Hi,
I am using Retina network security scanner ver 5.17. I have a license of 64 IPs. I have audited all 64 IP addresses now it is asking me to upgrade my license. Is there any possibility that I can remove the audited IPs and start scanning of IPs? I still have 4 months of my license remaining.
I have another network scanning software of other vendor it has the same limitation but it gives me the freedom of removing the audit IP and increase my remaining IPs.

Awaiting a positive response.