Short answer
Use a unit adder when every report needs the same extra amount, and use a percent adder when the extra should grow with the roof size or run length.
When To Use Add Extra
Use Add Extra when your normal formula is correct but the order still needs a little more material for waste, starter quantities, field handling, or common add-ons.
- Unit adders are best for fixed extras such as one additional tube, box, carton, or accessory.
- Percent adders are best when the extra should scale with roof size, roof area, or run length.
- Percent Add Extra is calculated before optional whole-unit rounding.
- If the formula subtracts more than it adds, the final quantity stops at zero instead of becoming negative.
Example
If underlayment is based on Roof Area SQ and you add 10 percent, a 30 SQ roof adds 3 SQ. If you add 2 units instead, that line adds 2 order units whether the roof is large or small.
Where To Change It
Open the Material Order tab, edit the Order Template, expand a material line, and use the Add Extra amount plus the unit/percent selector in the formula controls. Review the formula preview before saving the template.