Your number is current if your number is below the one listed for your region in the Diversity Immigrant section. There is also always an "advanced notification" section for DV of the next month. Once you see that your number is current there, you can wait a few days and then ask KCC about your interview date.
When it says "current", all the numbers for this region are current.
Remember, that DV is handled within a fiscal year. This means, the first interviews for DV-2009 start in October 2008, and the last possibility to get the immigrant visa is September 30, 2009.
If you have won in DV-2009, you can look through the bulletins of the last few years to see when you might be current.