Depending on the company's policy your initial deposit may be the part of the full cost. Thus you'll need to cover the balance between deposit and the total amount. Some car auction websites may request to place a security deposit, that will be refunded to you after you make the full payment.
When your initial deposit is taken as a part of full payment, be aware in advance how much time you have to clear up the balance left and try to settle the full payment within this period. Some auction websites let you only three or five days for placing full amount, and then penalty fees are applied.