runtime(doc): clarify the use of change marks when writing a buffer

related: #17008

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/autocmd.txt b/runtime/doc/autocmd.txt
index 372d1ac..820c302 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -1,4 +1,4 @@
-*autocmd.txt*   For Vim version 9.1.  Last change: 2025 Mar 12
+*autocmd.txt*   For Vim version 9.1.  Last change: 2025 Apr 03
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -593,7 +593,8 @@
 				The buffer contents should not be changed.
 				When the command resets 'modified' the undo
 				information is adjusted to mark older undo
-				states as 'modified', like |:write| does.
+				states as 'modified', like |:write| does.  Use
+				the |'[| and |']| marks for the range of lines.
 				|Cmd-event|
 							*BufWritePost*
 BufWritePost			After writing the whole buffer to a file
@@ -886,14 +887,14 @@
 FileWriteCmd			Before writing to a file, when not writing the
 				whole buffer.  Should do the writing to the
 				file.  Should not change the buffer.  Use the
-				'[ and '] marks for the range of lines.
+				|'[| and |']| marks for the range of lines.
 				|Cmd-event|
 							*FileWritePost*
 FileWritePost			After writing to a file, when not writing the
 				whole buffer.
 							*FileWritePre*
 FileWritePre			Before writing to a file, when not writing the
-				whole buffer.  Use the '[ and '] marks for the
+				whole buffer.  Use the |'[| and |']| marks for the
 				range of lines.
 							*FilterReadPost*
 FilterReadPost			After reading a file from a filter command.