Maximum Login IPs allows you to set the number of different IP addresses that the user can be logged in from, within a certain number of hours which is controlled by the other setting just below it “Maximum Login Window (Hours)“.
You can set the number of login IPs and hours window from Memberium -> Settings -> Login screen on Memberium admin dashboard.
For instance, if you set Maximum Login IPs to 3 IP addresses in 24 hours, then when you log in from a fourth IP address you would be denied until the timer ran out.