It is the boolean algebra behind the search.
If "9ct" is in the search then show the result. OK.
But if you wanted the search also to show "9 ct", then you need the search engine to disregard every single space in every search, which would be hopeless.
Ebid can also search in description as well as title. there is a choice on the drop-down menu, so savvy Ebidders might have all of 9ct and 9 ct and 9 carat in their description