In Excel 2013 the way to add Calculated fields changed a bit from the first version.
Now you click Power Pivot tab and click Calculated Fields and New Calculated Field. I preferred the old method where I could right click in the Power Pivot fields list and add or modify the measure directly to a table.
In the new I have to remember to set the correct table name in the first drop down box. In this case “Product” is the default table.
And yes – I tend to forget to change it sometime and my calculations typically ends up in the first table in the list.
So I decided to see if I could change it and then I found out that changing the order in the power pivot window had absolutely no effect on the default Table name and then it hit me.
That the Table name in the Calculated Field dialog was the FIRST table I imported in my model.
So if you want to control the Default table name – Start by importing the table you want as your default table for calculated fields.