witholding taxes on winnings

[obie1]

I was lucky enough to have (2) dollar tickets on the derby winning exacta does it make any tax difference if I cash them both in at the same time? How much will they take out in taxes each ticket is worth just over a thousand dollars. Someone told me they take out 25% is that of the amount over $600 or is it of the entire amount. Hate paying taxes when I finally have a winner.