Maximum Login Window (Hours) option is used along with the Maximum Login IPs option.
In the Maximum Login IPs option you’ll set how many IP addresses can user have within specific time frame. In order to set “time frame”, you’ll use Maximum Login Window (Hours) option.
As an example, if you want your users to not have more than 3 IP addresses within 24 hours you’ll set Maximum Login Window (Hours) option to 24 and in the Maximum Login IPs option you’ll have 3.
You can set Maximum Login IPs and Maximum Login Window from Memberium -> Settings -> Login screen.