Syn_, you don't see the chart at the bottom of the page, or you don't understand it?
What TL stands for just depends on who you ask.
My ex wife sats it stands for "terribly lazy",
An ex girfriend use to say it was "too long",
I had a neghbor once who thought it was "too loud",
I tell my current wife it means "tender loving",
On a bad day I think it must be "tough luck",
but "Trend Line" is what I had in mind, it seemed like a good idea at the time.
:0)