It searches the key and the string. So for example just searching for "new group post" finds the below.
Key: NEW_GROUP_POST_098c50
Text: New group post
Your sites name is prefixed by CBs notification functionality it self and not by CB. If you want that removed you have to translate the below string.
Key: EMAIL_NOTE_SITENAME_SUBJECT
FROM: [sitename] - [subject]
TO: [subject]