This property determines the initial size of the queue that holds messages received by Unity Multiplayer before they are processed.
Although the size of this queue is increased by Unity Multiplayer if required, it is useful to set up initial size of this queue with a sensible value to avoid this additional runtime memory allocation. The following formula is a good general guideline:
2 * max(topology.ReceivedMessagePoolSize) * hostNumber
Where topology is the HostTopology of the current network and hostNumber is the maximum number of hosts that can be open.