doc: mention maximum mark size in manpages
diff --git a/extensions/libxt_CONNMARK.man b/extensions/libxt_CONNMARK.man
index 571ce37..13c6b4b 100644
--- a/extensions/libxt_CONNMARK.man
+++ b/extensions/libxt_CONNMARK.man
@@ -1,4 +1,5 @@
-This module sets the netfilter mark value associated with a connection.
+This module sets the netfilter mark value associated with a connection. The
+mark is 32 bits wide.
.TP
\fB\-\-set\-xmark\fP \fIvalue\fP[\fB/\fP\fImask\fP]
Zero out the bits given by \fImask\fR and XOR \fIvalue\fR into the ctmark.
