A sell instruction is created when a trade is placed outside of market hours or during an intra-day auction. Your sell instruction will be converted into a sell trade when the market opens on the next trading day or once the intra-day auction has ended.
Take a look at the different trading hours for the account types below
USD trading hours are between 09:35 and 15:50 EST (23:35 to 05:50 AEST) Monday to Friday. USD trading will be closed on U.S holidays