Listen (-LSN)

Use the Listen adapter command (-LSN) for data sources to dictate the length of time (in seconds) that the MSMQ Adapters wait for one or more messages to be received. Map execution is suspended until the message is received or until the specified time lapses. The default value is S, meaning that the adapter waits indefinitely for a message to arrive in the queue.

-LSN {0|S|wait_time_in_sec}
Do not wait at all. If there is no input available, the adapter does not wait for more messages.
This is an infinite wait time.
This is the number of seconds the adapter waits for a message

For example, to specify a wait time of 30 seconds, the syntax would be:

-LSN 30