Forums Scripts & Popups Extracting(?) A number inside brackets (Simple.)

Hm, all people in the channel?

And I think it should contain some "cleaning", or the file will be ever-growing, containing many out-dated IPs.
Is there a message by the bot to trigger this? If not: under what circumstances should an IP be cleared - e.g. if the respective user parts the channel, or after a certain period of time?