The attainable rate you see now is no indication of the speed you will get under profile 17a.
The attainable line speed you see now is the speed you would get under 8C if the line was not capped at 40.
This is my take on it.
My attainable rate has also increased (it was 52 when I first had infinity installed). My modem was faulty so they replaced it and my line card / port was reset, but the BT open-reach eng was told while so was on the phone to BT wholesale that cabs are receiving a firmware update, this may be a reason for better stats.
What router/modem are you using to get them nice looking stats?
Sync 39999D 9995U
Attenuation: 9.6 SNR: 8.9
Line Length 300meters