runtime(doc): make 'shiftwidth' setting more precise

closes: #17414

Signed-off-by: Damien Lejay <damien@lejay.be>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index d69c204..cc0a5e6 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 9.1.  Last change: 2025 May 31
+*options.txt*	For Vim version 9.1.  Last change: 2025 Jun 01
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -7499,10 +7499,10 @@
 						*'shiftwidth'* *'sw'*
 'shiftwidth' 'sw'	number	(default 8)
 			local to buffer
-	Number of spaces to use for each step of (auto)indent.  Used for
-	|'cindent'|, |>>|, |<<|, etc.
-	When zero the 'tabstop' value will be used.  Use the |shiftwidth()|
-	function to get the effective shiftwidth value.
+	Number of columns that make up one level of (auto)indentation.  Used
+	by |'cindent'|, |<<|, |>>|, etc.
+	If set to 0, Vim uses the current 'tabstop' value.  Use |shiftwidth()|
+	to obtain the effective value in scripts.
 
 						*'shortmess'* *'shm'*
 'shortmess' 'shm'	string	(Vim default "filnxtToOS", Vi default: "S",