It has been suggested that I track my hub usage via Adsense, by setting up "custom URL channels", and that I can do this with up to 200 hubs. I have clicked on "URL trackers", but that seems to be something completely different. I've looked at all the pages under Adsense, but nothing there seems to be relevant to this.

My intention is to find a way of knowing which ads/hubs have generated revenue.

I'm confused! Help, please!

On your Adsense account you go to "Adsense setup" tab and choose channels from the menu there...

You want to use URL channels instead of custom channels.  Custom channels are for a different purpose.