It looks to me like this is what they sent you..........http://www.************/_preview.php?articleID=322
The box picture on the site you ordered from is for the Geforce 5900 Ultra 256mb. But nowhere in the description does it mention the amount of RAM. Also, at the very top of the page it says Geforce 5900 and nothing else. I am afraid they sent you what you ordered.
Their site does not go into enough detail about the product. With video cards getting more complicated these days it's up to the buyer to make absolutley sure they are ordering the correct product.
The price you paid for the card is a little high, I think you can get the same card in the lower or mid $200 range. But when they were first introduced they were about $400. The price you paid was somewhere in the middle of those 2 figures, so if you're satisfied with the card use it and have fun.