De-duplication of orders on merchandizing eVars is not done consistently.
If I do one purchase of two products, both using the same value in a merchandizing eVar (let's say: "shirts"), then
1. I see two orders for "shirts" in the eVar report (total line is 1)
2. When I do a breakdown to products, I see only one purchase for "shirts".
I do not disagree with either result. But it would be nice if you could restrict yourself to one method per report:-)