As b*cat surmised, your target SNR margin appears to be 12 dB, which may be the result of instability at some time. If this instability is no longer present, your target SNR margin could in principle be reduced to give you increased speed.
If you're intending to move to an LLU ISP such as TT or Sky, then this isn't worth doing anything about at this stage. The LLU ISP will have their own system for managing the target SNR margin. I don't know about Sky, but TT start you off at a target SNR margin of 12 dB, so if you move to them you'll very probably see a very similar connection speed initially, but with the possibility to increase it later.