I know that wordtracker is a daily count tool. Overture is a monthly count tool, but i do not know about keyworddiscovery. I'm sure if you send their customer service department an email with your question they can provide you with an answer.
bilalseo that is correct, overture has stopped updating their data center for their keyword count tool. Their statistics are over a year old. I do not know why they would do this as it has proven to be a useful tool to webmasters. Sometimes it seems as though the search engines are out to make our jobs harder then it already is. MSN stopped providing backlink information. Who knows what tools they will take away from us next.