diff --git a/draft-ietf-quic-transport.md b/draft-ietf-quic-transport.md
index b242445ee7..13c5542c5b 100644
--- a/draft-ietf-quic-transport.md
+++ b/draft-ietf-quic-transport.md
@@ -7413,9 +7413,16 @@ The initial contents of this registry are shown in {{iana-error-table}}.
 
 # Sample Packet Number Decoding Algorithm {#sample-packet-number-decoding}
 
-The pseudo-code in {{alg-decode-pn}} shows how an implementation can decode
+The pseudo-code in {{alg-decode-pn}} includes an example algorithm for decoding
 packet numbers after header protection has been removed.
 
+The DecodePacketNumber function takes three arguments:
+
+* largest_pn is the largest packet number that has been successfully
+  processed in the current packet number space.
+* truncated_pn is the value of the Packet Number field.
+* pn_nbits is the number of bits in the Packet Number field (8, 16, 24, or 32).
+
 ~~~
 DecodePacketNumber(largest_pn, truncated_pn, pn_nbits):
    expected_pn  = largest_pn + 1