In the rare case a market order sweeps the book and only partially fills, two Execution Reports will be generated: one describing the partial fill and another cancelling the market order as it was only partially filled.
Partial Fill Execution Report
Here is an example of the partial fill Execution Report:
CumQty: 1.0 is the total quantity filled.
LeavesQty: 42.978800000 indicates the unfilled notional value of the order.
CashOrderQty: 500.0 is the original notional value desired to be filled.
Order Cancellation Execution Report
and the following Execution Report representing a cancellation of the order: