Login Lockdown not locking out blocked IPs

I’ve got Login Lockdown enabled with a “Time Length of Lockout (min)” set to 999999. This is 694 days. (What is the maximum value for this field, btw? Is it possible to cause this feature to break if it’s set too high?)

However, when I switch to the “Failed Login Records” tab, I can see certain IPs appear multiple times in the list, much more quickly than they should be. The lockdown is not blocking offenders. What is going on?

Screenshot of the repeating IPs here: https://www.awesomescreenshot.com/image/19303788?key=1670b42064a4648e61070d71f5d7981f