"Has improper value for" is a predefined property to track input errors for irregular value annotations that was likely caused by type or allowed value restrictions and is provided by Semantic MediaWiki.
"Has processing error text" is a predefined property containing a textual description of an error and is provided by Semantic MediaWiki.
[[:2 × [[Kingfisher 33SP helicopter]]]][[Modification date::+]] (The symbol "[[" was used in a place where it is not useful. The part "]]" of the query was not understood.
Results might not be as expected.) +