How does Exchange2000_MsgsThroughSMTPService Knowledge Script total the inbound and outbound (NETIQKB26104)

How does the Exchange2000_MsgsThroughSMTPService Knowledge Script equate the number of inbound and outbound messages?

Exchange_MessagesThroughSMTP Knowledge Script returns different data than what the PerfMon counters for SMTP and Interscan stats show for the same time period.

The specific Managed Object function call that parses the specific Exchange Event IDs is called "GetMsgsThroughSMTPDomains". 

The specific event IDs being tracked are Event IDs 1019 and 1031, please reference MS Technet article: http://support.microsoft.com/default.aspx?scid=kb;en-us;311739

1019    SMTP Submit Message to AQ       SMTP: Message Submitted to Advanced Queuing
1031    SMTP End Outbound Transfer      SMTP: Ending Outbound Transfer

Formerly known as NETIQKB26104