Hi Carol!

You can control how the Index() (or any table calculation) is calculated using the drop down menu on the field:

Normally, if you have fields on Rows or Columns, Tableau defaults to Table Across (using the fields on Rows and incrementing the index for each new value) of Table Down (using the fields on Columns).  But when you don't have fields on Rows or Columns, or you need to override the default way Tableau computes the Index, you can change it:

By setting it to Specific Dimensions and checking both Category and Customer Name, I tell Tableau to increment the index for each new combination of the dimensions.  You might experiment with other options to see how it works.

Hope that helps!

Joshua