Can I just ask about the subject title

I looked at the wiki I am unsure. I want it set to a block time of 30 minutes after 3 invalid logins.

0 is disabled
Do I just put 30 in the box? Or do I put the symbol and number >30?

I tried both and it's not blocking me after trying 3 invalid logins.

Just to add, If I put 1 in the box it does block me for 1 minute. Is it that above a certain number it no longer works?