Why does the IP Profile drop?

[#1]

This is not a complaint as my speed is fine and connection stable. For many weeks my IP Profile has been 6000/6500 with throughput in the high 5000 kbps.
Last week I needed to check a friend's Netgear router which I did and then went back to my own (have been using this now for over one week).
Since then the profile has dropped to 5000kbps with speed in the mid to high 4000 kbps. Could someone please let me know if there is a reason for this (just out of interest)?

[#2]

Yes. 
It means that when you reconnected your router, it reconnected at a lower sync speed than it normally does, which caused the IP Profile to drop.  If you're now syncing at your normal speed, the IP Profile should pick up again.
I've covered it fairly extensively (I hope!) in my blog about broadband speeds.
link:speed

[#3]

Just a guess but when you connected your router again was it in the evening when the interference on the line was worse.
Try resynching the router in the middle of the day and see if the sync speed increases

[#4]

Right, first of all I will do the re-synching as it is the middle of the day and see what happens. Also, will take a look at the blog (which I probably should have known about anyway  :-[).
Thank you both for the advice.

[#5]

Foillowed advice and after a couple of days profile is back up to 6500. Speed not caught up yet though - still in the mid 4000's whereas before it was high 5000's - hopefully will catch up. Noise margin down too so all advice was absolutely spot on. Thank you all.

[#6]

is the 6500kbps figure your new ip profile or your new sync rate as if its your profile inceased i find that i have to disconect internet and reconnect for the new profile to work(get the new thoughput increase). only disconnect from plusnet thoe dont do a resync or you might end up back at sqaure one again.
on the netgear you do this by going to the stats page and use the connection tab

[#7]

Actually am back on the Thomson now. Had a connection drop this morning (extremely unusual for me). Re-booted the router and just now have done a PN speedtest which has come back up to 6114 kbps so am pleased that things are back to what they were.
Thank you for the adavice Asbo Dog - am learning all the time.