Strange email about speed estimate

[#1]

Hi,
I have been with PN for 14 days now and this morning received an email from them with a comparison of speed estimate vs actual speed.
In the email this is the summary:
Estimated line speed: 3.5Mbps
Current line speed: 15Mbps
When I signed up, the estimated line speed I was given was 20Mbps (due to living so far from the green box), so where does the 3.5Mbps come from?  Given that the estimate was originally 20Mbps (which the engineer confirmed when he installed the line), is 15Mbps an acceptable speed?
Can any PN agent please comment on this?
Username = jazbur765
Thanks, Jason

[#2]

The estimate is for ADSL not fibre - stupid isn't it

[#3]

That explains it then, thanks for the help, it does seem very strange though to quote adsl speeds.
Still the actual speed is 25% less than estimated, is that within acceptable range?  I need all I can get given the maximum speed of the line 
Cheers.

[#4]

What is the estimate here http://www.dslchecker.bt.com/adsl/ADSLChecker.TelephoneNumberOutput
Plusnet base their estimate on the lower of the clean speeds
However the BT clean estimate ignores line quality problems and, according to one BT engineer, that includes lead sheathed cables as well as aluminium cables

[#5]

On that BT checker
FTTC Range A = 30 (high) and 20.7 (low)
FTTC Range B = 23.5 (high) and 11.4 (low)

[#6]

It could potentially be that you fall into the B range rather then the A range.
The only way we can really investigate would be to send a engineer although I can't promise that they could increase it.

[#7]

Hi Matthew, thanks for the reply.  I'm happy with the speed and service, no problems at all.  I'm getting wireless speeds of 14-15Mbps, compared to what I was on before, I'm looking at 6X the speed, so that will do me  :).
If I hadn't of received that email then I wouldn't have been in touch at all.
Cheers.