If you would like to receive an email warning of your server approaching maximum concurrent sessions, enter the number of sessions "from the top" or maximum, at which you would like to receive an email from the Inventu Licensing server (at Inventu.com).
This will be sent to the email associated with your license (also used to send notification of a subscription renewal).
Note that for this to work, your Firewall must have port 443 open to Inventu.com as the email is triggered by a web service call from the Inventu Viewer Emulation Service.