We have the following measures:

The formula for the measures are:

For Order Count, we use COUNTD([Order ID]), because Order ID is NOT unique in factOrders. Some OrderID has more than one products. That I why OrderID is not unique.

For Customer Count, we use COUNT ([CustomerId (dimCustomer.csv)]), because CustomerId is unique in dimCustomer

We can do operations between an aggregated and row-level measures. The created measure is also at the same level of operants. For example,

Order Value Avg = [Gross Revenue]/[Order Count].

Both [Gross Revenue] and [Order Count] are aggregated and therefore, [Order Value Avg].

Profit Margin % (Row Level) = ([Revenue]-[Cost])/[Revenue]

[Revenue], [Cost] and [Revenue] are row-level and therefore [Profit Margin % (Row Level)] is as well.