A receipt for what the system costs, with a QR to the action. Sized for an 80 mm thermal roll, the kind in a cafe till, so people walk away holding the numbers. It also prints fine on A4 as a narrow strip you can cut down.
Thermal printer: set paper to 80 mm and print at actual size.
Normal printer: print on A4, then cut the strip.
Every figure carries its source. Do not edit the numbers by hand.