License not releasing unused IPs, even after a few weeks

Hello everyone,

I am a fresh adopter (switched from pfSense a few months ago), and found ASG to be a wonderfull product.
I'm using the software version, with a home license.

I'm facing a little issue at the moment : the license counter tells me that 49 IPs (of 50 available within the license) are used.

I know that unused IPs are supposed to be "released" 7 days after they've been seen for the last time.
However, I'm still seeing old IPs in the "active IP addresses" tabs, even weeks after I've shut down the corresponding machines!
(And I'm pretty sure these machines are fully shut down for more than 7 days, for they were VMs on my laptop that I erased last month)

Is there a way to refresh this "active IP addresses" counter?
I've read in the forums a few tricks, such as reinstalling the software and restoring a backup, or simply restoring a backup at boot time (with a clear backup at the USB key's root).
I'm not very pleased to perform the 1st option, and I don't know how to launch the 2nd one : when I start the machine with a USB key containing the backup, it boots normally. Nothing happens (backup is on the key's root directory, has no password, key is a 8 GB model, fat32-formatted).

Could someone provide me a little help here, please?
Thanks a lot in advance!