The 1855 targetry was all an iron plate, 6 ft tall, by 2 ft wide.
It had an 8 inch bull, with a 24 inch magpie/inner. The targets were whitewashed iron, with a black painted bull and magpie ring, painted within grooves in the iron. (as such this generator makes a 3/4 inch thick ring.)
Since these targets were on a white background, you may scale either the entire target to the page size and orientation you select, which will print lines on the side indicating the scaled target boundaries, Or you may choose to print only the target centre, which will then scale the bull and magpie ring to fit your paper, and tell you how big a white paper you need to place this printed object in the middle of to be the correct size.