2 lines - 2 different ADSL Max estimates?

[FunkyT]

I realise it's not an exact science but the BT Checker displays the following:

Line 1 - 5.0 Mbps
Line 2 - 5.5 Mbps

Any idea how this is measured?

I've ordered Max on Line 1 so should have some idea by the end of the month...

 

[Burbleflop]

I get wildy different guesstimations for the 3 lines I have coming into the house. Not sure what causes it since I'd expect the cables to take the same route back to the exchange.