EmailXtender Total Message Count

I have two questions related to the total msgs count displayed in the EX Admin Console

The answer to the first may explain the second but here they are:

1)     How is that number calculated?

2)     What would cause thant number to be different from the md5hash count from the SQL Message or VolumeMessage Tables?

In both causes I've seen recently, the EX Admin Console reported lower than both of the above table counts.