To enable cross-filtering, click on Manage Relationships from the home ribbon; this will launch the manage relationship editor. Find the relationship between FactInternetSales and DimCustomer, and then click Edit.
Once the relationship editor has launched, change the cross-filter direction from single to both:
Figure 14- Changing the Cross filter direction
Back in the report view, you will now see the correct customer count for each product:
Figure 15-Customer Count for each product
Do not enable cross-filtering for your date table. In order for some DAX calculations to work properly, the date table must have a contiguous range of dates.