This is a buttoned sleeve cuff. If it is part of a garment, the circumference of the cuff will be set by the sleeve, otherwise the Band Circumference variable must be entered manually. Band Circumference should be the measurement around the arm where the cuff will sit.
The draft will add Wrist Ease and Extension Width to accommodate the overlap needed for the button.
An additional 1/8" / 3mm will be added to the Button Diameter to calculate the buttonhole size.