FTTC Clean and Impacted

[#1]

so have checked the availability on my cabinet and get the following results.
what's the significance of clean and impacted?
the telephone pole is about 30 feet from the house and the cabinet is another 30 feet or so from the pole.

[#2]

"Clean" is where the last section of copper line from the cab to your property is in good condition. "Impacted" is when it isn't.
Until you get your fibre actually connected, you won't know.
Mine shows:

                       High Low High Low 		
FTTC Range A (Clean)    80  69.3 20  19.9 -- Available
FTTC Range B (Impacted) 80  55.9 20  17.9 -- Available

The Member Centre shows this:

Estimated line speed: 69Mb
(Download speed could vary depending on line conditions. Estimates are the maximum speeds that your phone line can support.
These speeds are dependent on the package you choose.) - Checked on 2014-05-03 02:03:00
Current line speed: 65.2 Mb

So, the estimate was at the Low end of the Clean range.
My actual speeds are OK, in fact as I am quite a distance to the cabinet, I wasn't expecting too much. I'm the first on my cab, according to the installer¹.

¹ I won't call him an engineer as he was a contractor, but did his job OK.