Nothing wrong - the noise margin is low, so when estimating how much more speed you can get it not give a good figure. Hence why I also give a figure based on the lines attenuation, which is around 3800Kbps. Pays to read the full text.
The low margin is probably because you are on a fixed speed product, and power levels are held back
from
www.farina1.com/adsl
Your maximum line connection speed using an ADSL (up to 8Mbps) service is: 1764Kbps
If using a BT Wholesale Max product, then your expected IP Profile (sometimes called BRAS Data Rate) will be. 1.5Mbps
The IP Profile is set based on the lowest speed seen in the last 5 days, it drops immediately, but may take 5 days to improve even if you reconnect at a good speed again.
If your service provider uses ADSL2+ the maximum line speed likely is: 7203Kbps
With ADSL2+ the maximum IP throughput (result from a speedtest) is likely to be around: 6374Kbps
It would appear your line is under performing with regard to ADSL, this may be due to issues like the ring wire, unfiltered equipment and other factors. Ideally you would expect to see connection speeds of 3800Kbps or higher at your attenuation
Your ADSL2+ speeds are likely to be in the range 4850Kbps to 7900Kbps. With the line under performing with ADSL, it is likely this will hold back any speed increases the checker is suggesting for ADSL2+.
If your ADSL or ADSL2+ connection speeds are slow for the attenuation of your telephone line then take a look at this guide to removing the ring wire from your extensions.