Evaluating cube SQL that creates Measure

I am using Visual Studio 2008 Analysis Services and processing the AdventureWorks database to create and process a cube.  One of my measures is the Sales Amount field from the FactInternetSales table.  When I click and drag that field onto an otherwise blank crosstab, my value is less than 29358677.2206503, which I know it should be.  The study video I'm following shows that value, as do I when independently verifying the value by writing a view against the table.  

I suspect that when the measure is defined, something in the SQL statement puts a filter on the field, resulting in a value that is too small.  I do not know how to test this hypothesis.  Please help.

Thank you, ~Peter Ferber