What price can I set, and how long does my auction run?

The price is a starting price, not a fixed price — bidding opens there and goes up. Enter it in whole CRETA (no decimals), up to a maximum of 100,000,000.

The length of the auction is not yours to choose: it is a setting on the auction contract for that collection, and the item's page shows the countdown once the listing is live.

There is no reserve price beyond the starting price you set, so set it at the lowest figure you would genuinely accept.