Update example-block.mdx

website/pages/partials/from-1.5/builds/example-block.mdx

@@ -11,7 +11,8 @@ build {
     source "source.amazon-ebs.example" {
         # Use the singular `source` block set
         # specific fields.
-        # Note that values cannot be overwritten.
+        # Note that fields cannot be overwritten, in other words, you cannot 
+        # set output from the top-level source block and here.
         output = "different value"
         name = var.foo
     }