Help me understand how recoding buffers work for multiple channels

I'm trying to understand how it works, but still am unsure. I have a TiVo Bolt.

I'm used to the last 2 channels watched, since my last box from BrightHouse was a 2-tuner, to be recording up to an hour in the past. It was great

Now I have 4 tuners, yet I have yet to see any recording buffer on anything other than the channel I have it on. Is there something I need to do or what? How does this work?

Thanks.