Transmitting data from a Sleep Support node to a sleeping network

Page 51, XBee-PRO S3B User Guide says:
Synchronous Sleep Support Mode (SM=7): A sleep support node will only transmit normal data when the other nodes in the sleeping network are awake.

If I send serial data to the mains-powered Sleep Support node (also acting as the sleep coordinator) while the network is asleep, does it BUFFER the data until the network wakes up?
Or does it DISCARD the data??

The User Guide does not say.

It will buffer the data and send it when the network is awake.