You can use our script to check the number of UniFi devices connected to your server.
First, you'll need to get SSH access to your server: https://support.hostifi.net/en/articles/3437198-how-to-ssh-or-sftp-into-your-unifi-server
Then, run this:
mongo ace --eval "db.device.count();" --port 27117 --quiet
It will output the UniFi device count to the terminal.
Alternatively, you can check UniFi device count from network.unifi.ui.com: