In the same way that you don't keep a tab on how many phone calls you make, or how many items you put in your basket at Tesco's?
Life is full of watching what we do, we watch what we eat, what we buy, how much we spend etc.
If you're not a BIG downloader you're not gonna need to keep watching it, so don't fret. If you are a BIG downloader then maybe you should consider moving to ADSL and leave ntl
Please do!