Setting initial ADSL2+ Profiles a question out of curiosity

[#1]

PN have my initial profile set to 17000, whilst incidentally BT still has 5000 (ticket raised for investigation by BT and  subject aired in another thread).
What I am curious to know, is how (methodology used) the initial IP profile is assessed.
Any takers to relieve my ignorance!?
dick:green Title fixed.

[#2]

OK, whats the first word of the Title, cant find it in my dick shun ary

[#3]

"Setting" it should be,
Why do the message board sadists make it impossible to amend a title: it's a severe discriminatory act against us tripeists.

[#4]

It's your initial post lucerne so you should be able to edit the post and it's title by clicking 'Modify'.