What is (daily) "My friends can challenge me no matter what"?

I just noticed this "My friends can challenge me no matter what" button under "Daily Chess" in my profile.

What does "no matter what" mean?

It's turned off - but friends have been challenging me to games with no problem up to now, so I'm worried about the "no matter what" designation.

I tried using "help" and Googled it, but didn't find an explanation.

You can set it up so that only certain ratings can challenge you. If your friends fall outside of those ratings, that setting would allow them to still challenge you.

It may also allow challenges from friends if you have the unavailable setting on, but I'm not sure on that.

Hmm, looks like the unavailable setting isn't there but if you have the Max Games set and are already at your max, your friends could challenge you. I'm guessing setting that at 0 is the same as being unavailable now.