CB Activity and Cleanup

Hi
Apologies, but can you just clarify how the Cleanup function in CB Activity works, please? I can see it can be set up to (I presume) delete older activity after chosen intervals, shown on a drop down list. It also appears that this can either be scheduled using CRON or maybe activated by clicking the highlighted link "click to process"? Is this link supposed to clear activity older than anything chosen in the drop down list?

There is also a mention of "your site unique URL", and I'm not sure where this comes in, or what its referring to? When I click on the link, a blank page appears with an address in the browser window. I'm missing something obvious but I can't see what.

It's a URL unique to your site (it uses a security key unique to the site) that deletes activity outside of the duration specified. So if the duration is set to 1 year and you use the URL it'll delete anything that's older than a year. You'll always get a blank page as it's meant to be ran with CRON and has no output, but can be ran manually.