UCR201: 1-15 selection if you hold Home + Goto Zero

[Matt]

On the UCR201 if you hold Home + Goto Zero it exposes a few options that I can't find documented anywhere. You can select from a range of 1 to 15.
I don't think it's the channel selection, as that is shown when you hold F1 + F5.

I've been over the manual a few times and see no mention of it. Does anyone here know what this setting is?

[RsX]

You got me curious
It turns out it is a fine RF calibration
https://www.cncdrive.com/forum/viewtopic.php?f=4&t=4946