correct help text of Label field => can be a Label Expression

war/src/main/webapp/help/tools/help-label.html

 <div>
     Optional label to restrict the use of this installation method.
-    Only nodes which have this label will be considered.
+    This label could be a Label Expression (for example : "linux&&x64" or "windows&&x86").
+    Only nodes which validate this label (or label expression) will be considered.
 </div>