TX powers, with picture

Attached is a snapshot of the TX powers tab of a wireless interface, with ‘default’ selected.

Could someone explain what I’m looking at here?
TX.jpg

That is manual, not default.

I’d selected manual to get the ‘readings’ but not applied it so the card was still set to default and I’d assumed these were the ‘default’ settings.

But what does it mean? What is the ‘Tx powers’ table showing everything at 17dBM indicating? What’s the relevance of ‘current Tx powers’? Why would I want to change anything here and what would happen if I did?