diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index eece600..3d1f2ff 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -7776,7 +7776,10 @@
 	      mark.  This information is used for mouse clicks.
 	< -   Where to truncate line if too long.  Default is at the start.
 	      No width fields allowed.
-	= -   Separation point between left and right aligned items.
+	= -   Separation point between alignment sections.  Each section will
+	      be separated by an equal number of spaces.  With one %= what
+	      comes after it will be right-aligned.  With two %= there is a
+	      middle part, with white space left and right of it.
 	      No width fields allowed.
 	# -   Set highlight group.  The name must follow and then a # again.
 	      Thus use %#HLname# for highlight group HLname.  The same