I'm not too familiar with awstats my self but on their website they have this in their wiki:
Errors
If you get the following error similar to the following after updating the robots file...

• Error: Not same number of records of RobotsSearchIDOrder_listx (total is 789 entries) and RobotsHashIDLib (787 entries without 'unknown') in Robots database.

You've probably added a duplicate robot entry, which will need to be removed/merged with the existing entry - search your backup robots.pm file for a robot that you're trying to add.

boushehri, 

did you ever solve this? I'm getting the same error you had

Well for me it was saying 1106 entries in RobotsSearchIDOrder and 1105 in RobotsHashIDLib, so I added ('unknown') in RobotsHashIDLib and seemed to work. I will have to wait and see if 24 hours brings any statistics or errors.