Embedded BI template and Sum of Page totals

I am using page totals by the add-page-total and show-page-total syntax, which is working correctly. I have two variables, tb for total bottles, and tc for total cases. I want to add the value from each for a total pieces. I have tried to follow the XML Publisher Core Components Guide. On page 2-74, 2-75, the example is almost exact for what I want to do except I want to sum instead of net. I just don't get anything other than zero.

This Works:

<?SOQS_Quantity_Shipped_CA_ID162?><?add-page-total:tc;'SOQS_Quantity_Shipped_CA_ID162'?> (This is in a variable on the detail for-each loop)