diff --git a/index.bs b/index.bs
index d80e923..552cfa3 100644
--- a/index.bs
+++ b/index.bs
@@ -1585,6 +1585,7 @@ The dictionary SHALL have the following members:
 :: True if the rate at which queued data will be sent by the user agent on all streams
    that share a [=WebTransport session=], as calculated by the
    congestion control algorithm, is considered limited by back pressure from the server. Otherwise false.
+   This is based on the server receive window.
    Datagrams MUST NOT be included in this calculation.
 : <dfn for="WebTransportSendRateStats" dict-member>inSlowStart</dfn>
 :: True if the current congestion control algorithm implements "slow start" and the