Moving-Total Not Working

[fry]

Hello

This question is in respect to Dynamic Cube Designer.  I am trying to create a measure which is based on an existing measure (Quantity).

The expression I am using is moving-total(Quantity,2).

The expression validates and the cube start up good. Issue is when I view my data against time I cant seem to understand how the moving total is being calculated. When I do this against a relational package, I see how it is using the current row and previous row values, however in Dynamic Cube I cant find how its being derived
Quantity    Moving_Total
914,965, 18,929,203 Jan 12, 2010
250,386       500,736 Jan  13, 2010