Westnet internet?

I am trying to understand a certain section of westnets website, and I was wondering if anyone could help me understand.

Their website is here

Alright so I was origionaly looking at the "Boost Plan" but then I saw the "Pro Plans" and I am trying to understand why it says 1.5Mbps To 20Mbps download speed, why not just one speed?

Thanks alot for your help.

Your speed depends on your distance from the exchange, and the quality of the copper, etc...

How do I find out how far I am from the nearest telephone exchange and the quality of the copper?

Kent.