Zend certified PHP/Magento developer

Where does znc keeps its channel logs and how do they interact with the client?

So I am trying out znc, a popular IRC bouncer and hexchat. Apparently znc keeps the logs and sends to hexchat each time.

What I don’t get is, how does hexchat know not to show me duplicate logs (its own local logs + the ones that just got sent)?

Where are the logs stored? I have tried deleting the local logs (the ones in appdata) as well as rebooting the server, but hexchat still shows me the logs.