Update README.md

README.md

@@ -275,7 +275,7 @@ Provides per application events.
 #### Packet callbacks
 Provides per packet events.
 
-`PacketFreeCallback(Packet packet)` notifies when a packet is being destroyed. A reference to the delegate should be preserved from being garbage collected.
+`PacketFreeCallback(Packet packet)` notifies when a packet is being destroyed. Indicates if a reliable packet was acknowledged. A reference to the delegate should be preserved from being garbage collected.
 
 #### Host callbacks
 Provides per host events.