Error for duplicate entries in "wp_domain_mapping_logins"

[15-Aug-2014 19:21:43 UTC] WordPress database error Duplicate entry '2c58828fffc36d98b5kf62ca6ea0f23b' for key 'PRIMARY' for query INSERT INTO wp_domain_mapping_logins (id,user_id,blog_id,t) VALUES( '2c58828fffc36d98b5kf62ca6ea0f23b', 0, 5, NOW() ) made by require('wp-load.php'), require_once('wp-config.php'), require_once('wp-settings.php'), do_action('init'), call_user_func_array, ITSEC_Lockout->check_lockout, ITSEC_Lockout->execute_lock, wp_logout, do_action('wp_logout'), call_user_func_array, remote_logout_loader

It mentions “Lockout” which I figured is associated with this plugin. I got more than 100 instances of it within five minutes.

A few days ago I got several more of this as well.

I deactivated and reactivated the plugin and until now haven’t got it again but I will wait and see.

Regardless, I really want to know what exactly does this error mean?

https://www.ads-software.com/plugins/better-wp-security/