Fixed UPGRADING

Added a concrete example regarding the change in which the number of digits
rounded by round() was extended by one digit.

Author: SakiTakamachi

UPGRADING

@@ -559,8 +559,10 @@ PHP 8.4 UPGRADE NOTES
     certain numbers, so this fix removes "pre-rounding" and changes the way numbers
     are compared, so that the values are correctly rounded as decimal numbers.
   . long2ip() now returns string instead of string|false.
-  . The maximum precision that can be handled by round() has been extended by
-    one digit.
+  . The maximum precision that can be handled by round() has been extended by one
+    digit. For example, if rounded 4503599627370495.5 with precision -1, would expect
+    it to result in 4503599627370496, but previously this was not the case and no
+    rounding was done.
   . output_add_rewrite_var() now uses url_rewriter.hosts instead of
     session.trans_sid_hosts for selecting hosts that will be rewritten.
 
@@ -801,7 +803,7 @@ PHP 8.4 UPGRADE NOTES
   . P_GID (NetBSD/FreeBSD only).
   . P_SID (NetBSD/FreeBSD only).
   . P_JAILID (FreeBSD only).
-  
+
 - Standard:
   . PHP_ROUND_CEILING.
   . PHP_ROUND_FLOOR.