BT line Speed derived from ISP line speed?visaversa?neither?

Question as title really. When I do a BT Performance test it gives me the current speed and the IP Profile which I believe is meant to be the same as the ISP figure for current line speed. I thought I read somewhere that throughput can never be greater than the ISP current line speed so if I have an ordinary speed test of say 5.2 and a ISP current line speed of 5.5 but a BT IP Profile speed of 6.5 is it likely that the ISP current line speed will move up to the BT held IP profile speed of 6.5 or will the BT held IP Profile speed be moved down to match the the ISP current line speed of 5.5?
I guess if I wait 3/4 hours I may be able to answer my own question but as we will then be in night noise period it may be a new ball game.

Sync determines the IP Profile.

When the IP Profile changes the ISP should get an automatic notification to change their Current line speed. They usually change it to a fraction below the IP Profile. The ISP change is usually a few hours later and should always be well under 24 hours later.

For whatever reasons, that notification or automatic update of the ISP one can fail. If that happens then the ISP one will stay incorrect until the next IP Profile change, which will only be when you have a re-sync.

Note that a downward IP Profile shift can also fail to update the ISP copy. In which case it is the IP Profile that determines the maximum throughput. It is always the lower of the two, as BT Wholesale limit it to the IP Profile.

Thank you
That clears that up and good news is ISP figure has gone up overnight so rein, noise
thunder, bad joints, leaves on the track,dlm permitting my throughput should be better.

Great.

It's worth adding, I should have said that if the auto-update fails the ISP can obviously set their version correctly. If you get hold of someone in support who understands the issue.