When you perform a search, whether that is the regular or wildcard search, you will see the keyword preview window before you commit to spending credits.
The keyword preview window shows you a sample of the keywords that will be returned and allows you to filter out unwanted categories or keywords.
Currently, only the regular search supports the word filters.
Once you are happy with the keywords, click Get Keywords, which will consume your credits. If you decide to cancel your search, no credits will be used.