-This module matches the length of a packet against a specific value
-or range of values.
+This module matches the length of the IPv6 payload in octets, or range of it.
+IPv6 header itself isn't counted.
.TP
-.BR "--length " "\fIlength\fP[:\fIlength\fP]"
+.BR "--length " "[!] \fIlength\fP[:\fIlength\fP]"