diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 008926f..be53e9f 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -5063,11 +5063,26 @@
 			omitted, there is no extra character at the end of the
 			line.
 							*lcs-tab*
-	  tab:xy	Two characters to be used to show a tab.  The first
-			char is used once.  The second char is repeated to
-			fill the space that the tab normally occupies.
-			"tab:>-" will show a tab that takes four spaces as
-			">---".  When omitted, a tab is show as ^I.
+	  tab:xy[z]	Two or three characters to be used to show a tab.
+			The third character is optional.
+
+	  tab:xy	The 'x' is always used, then 'y' as many times as will
+			fit.  Thus "tab:>-" displays:
+				>
+				>-
+				>--
+				etc.
+
+	  tab:xyz	The 'z' is always used, then 'x' is prepended, and
+			then 'y' is used as many times as will fit.  Thus
+			"tab:<->" displays:
+				>
+				<>
+				<->
+				<-->
+				etc.
+
+			When "tab:" is omitted, a tab is shown as ^I.
 							*lcs-space*
 	  space:c	Character to show for a space.  When omitted, spaces
 			are left blank.