Cables requiring maintained spacing (25% / 100% of Ø) are arranged in a single layer resting on the tray floor — they are never stacked, since stacking would block the free-air clearance the spacing exists to provide. Cables with no spacing requirement (0%, bundled) are grouped in their own zone beside — not on top of — the spaced cables, and may stack among themselves. Where a spaced cable sits at the edge of the bundled group, the required clearance is still maintained on that side. Area fill is checked against the commonly referenced 40% guideline from NEC 392.22 / CSA C22.1. This tool is a design aid — final tray sizing should be verified by a licensed electrical engineer against the applicable code edition and AHJ requirements.