Silicone-jointed glass-to-glass conditions should be sized from the published add-on or deduction chart for the exact joint type. The reference pages you attached show how 90°, 135° and 180° joints behave differently.

Joint-specific logic

A 90° corner, a 135° mitered return and a 180° inline butt joint do not share the same add-on. Each joint geometry changes the amount of glass required to achieve the intended overlap, butt or miter condition at the planned silicone gap.

Common mistake

Do not deduct the nominal silicone gap twice. If the manufacturer chart already assumes a standard joint gap, use the chart as written and do not subtract that gap again in the base calculation.

Multiple joints

If a piece has different joints on each side, calculate each side appropriately. One piece may need a positive add-on on one side and a different condition on the other.