UPC, for up to 250 mb/s.
A lot of things can affect it. Somebody will be along presently who knows what they're talking about, but:
1. What is your wireless card? Configured properly?
2. Wireless carries better in different environments. In my lump of oversized concrete it is shite.
3. How many connections on the box
4. Interference from other wireless.
5. Time of day
I have the same package for a mythical 250 MB. You will never attain anything like that anyway. Average download for me in the city 70 MB wireless/130 MB cable. Download speeds average 6 MB/sec.