IP Address Ranges for Blocking

In IThemes Security I would like to block the IP Ranges for specific countries, I am unsure how to show the ranges correctly.

I have tried a few combinations, but keep getting errors.

For example:

111.111.11.0/255

and

111.111.11.0-255

Neither work.

Can someone confirm the correct way to show IP Ranges in IThemes please?

https://wordpress.org/plugins/better-wp-security/