Are you sure it's "at least"? typically ISPs will say "up to" a specific speed so they can protect themselves from people not "getting what they pay for".
Well I spoke again with my ISP via live chat and they said that they theoretical speeds. They also said I could be better off with Cable over ADSL2 and the nearest exchange is 5.8km and the consultant said I should get 3-4mbps on ADSL2 but the NBN will hopefully be available in February next year so I should be getting speeds of atleast 25mbps down..
I cannot wait 6 months for faster internet. Under the previous Labor it would've been fiber all way including to the premises but now that we have a Liberal government they've made some savings and getting it done faster. Instead of every premises getting fibre from what I've read there will be a node in every street, So we will still be using the existing copper network.