clarify that no batch process is assumed in examples.

fixes #309

Author: mirjak

draft-ietf-quic-ack-frequency.md

@@ -392,6 +392,9 @@ ACK_FREQUENCY frames.
 
 ### Examples {#examples}
 
+Note that the following examples assume that packets are processed one-by-one in the received order
+as indicated below.
+
 When the reordering threshold is 1, any time a packet is received
 and there is a missing packet, an immediate acknowledgement is sent.