I got more or less the same thing, only i use ThreeWP Activity Monitor for logging. I got probably a few thousand although my logs are limited to contain 1000 entries max. Lucky thing I don't have an admin user.
It seems not to work 100%,
My settings are:
Lockout 5 allowed retries
20 minutes lockout
4 lockouts increase lockout time to 24 hours
12 hours until retries are reset
But 1 and the same ip adress achieved to made 999 tries, according to the 'ThreeWP Activity Monitor' plugin. Probably it was more but logs are limited for 1000 entries.
Nice adition would be that there are at least 30 seconds between an single entry