I believe NB means "Note well" That is, pay attention or important notice here. It is Latin for "nota bene"

Note that scaleFactor is not used in MyButtonStyle. It can be eliminated. Looking at my actual application, the exampleView looks like the following: .buttonStyle(GameButtonStyle(labelWidth: 140 * scaleFactor, labelHeight: 20 * scaleFactor, minWidth: 70 * scaleFactor, verticalPadding: 3 * scaleFactor)) I determine the scaleFactor depending upon the size of the window on OSX or the size of the screen on IOS.