Speed in "High Speed Broadband"

[#1]

How does the speed shown in the portal compare to the rate set by BT?
I recently had interleaving removed from my line and my router now shows that I'm synced at 8128 and the BT speed tester shows a line rate of 7150.
Before interleaving was removed I synced at a lower rat (7616?) and had a line rate of 6500.
However, the speed on the portal showed 8000 when I had a line rate of 6500 and is now showing 7000 against a rate of 7150.
It's not really a problem - I'm just wondering how the PlusNet portal rate tracks the BT set rate.
Edit: typos

[#2]

Hi Paul,
This is something that we have recently implemented.  We now restrict your traffic to roughly 7125Kbps at our end when you have an IP Profile of 7150Kbps.  this is because the QoS on our network is more effieicent than on the BT network.  So by limiting your traffic to just below that of the IP Profile, your throughput speeds are potentially fractionally higher.
It's nothing to worry about and is actually an improvement in potential service levels.

[#3]

See the discussion on this here and some speed testing that PN did here.

[#4]

Thanks for the replies.
As I said - it isn't an issue, I was just curious as to how the system works!