Your shares stay in the book until a buyer fills them or you cancel. Cancelling is always open to you, and what is left comes straight back to your wallet.
A fill is priced from the live mark at that moment, less your discount. The USDG shown here is an estimate at today's mark, and it moves with the market until you are filled.
Outside US trading hours a price feed can sit still for hours while the real market moves. A listing is always filled from the feed, so choose your level with that in mind.