How the Search Engine Works

Search is executed by relevance, meaning it works through a point system that accumulates based on how many times the searched word appears in each record.
Records with the highest points are placed at the top of the results list.
However, not all matches score equally. A match in fields such as the title or the author scores higher than others. In addition, extra points are awarded when what the user has typed exactly matches the record's metadata.

In the example of the book "Invisible," all records that have 245$a = Invisible appear first because the text searched by the user exactly matches the title of those records.
However, there is a book with 245$a = Invisible (illustrated edition) that does not appear at the top because its title does not exactly match what the user searched for; it contains additional text.
Since it does not exactly match, that record scores the same as any other that contains the word "invisible" in the title.

The information "(Illustrated edition)" should not be in the title because it is not part of it. The MARC format has other specific fields to include that information.