When placing market order, you can indicate additional conditions in the "Fill Policy" field of the trade page:
● Immediate or Cancel (IOC)
In this case a trader agrees to execute a deal with the volume maximally available in the market within that indicated in the order. In case the order cannot be filled completely, the available volume of the order will be filled, and the remaining volume will be canceled.
● Fill or Kill (FOK)
This fill policy means that an order can be filled only in the specified volume. If the necessary amount is currently unavailable in the market, the order will be canceled.