The variables that appear here are determined by the formula selected in the Assemblies Header. Enter a number in the Quantity field on each line. The default is "0.00".
The list of items included in the assembly and their quantities and costs. Review the quantities to see if they match your expectations. If they do not, try adjusting the Quantity field in the Assemblies Details Tab and/or the Calculation / Quantity field in the Formulas record linked to the assembly and run the test again.
Note that the Quantity column does not appear in the Items Table until you click the Calculate button.