Print calibration sheet
Print this page at 100% scale (disable "fit to page"). Then measure the square and the ruler with a physical ruler. The square must be exactly 100 × 100 mm. If it is off, adjust your printer's scale setting by the same percentage and reprint before cutting any dieline.
↑ Reference square: exactly 100 × 100 mm (diagonal ≈ 141.4 mm)
↑ Ruler bar: 100 mm total, ticks every 10 mm