Thats a US website so I'm afraid has no bearing over here at all
The UK Silver Fox is a different rabbit entirely!
OP your bunny is an Argente of some sort - either a Noir or a champagne - I hope its noir as champagnes are HUGE! they start off black as babies and silver up as they get older so in a few weeks hey will be enitrely silver with that lovely black undercoat when you blow into it. Beautiful.