Are all 4 Web Viewer Servers pointing to the same database? While you can have 4 Web Viewers pointing to the same database, the Web statistics may not be accurate.
If they are, in the Getting Started manual, under Installation Scenarios (page 14) with multiple Web Viewers running on separate computers sharing the same database is the statement:
"Note: The web statistics may not be updated properly with this installation option."
Otherwise, you should use statistics from DRAS to get a more accurate count.