Generally, you draw objects at their actual size. When you plot the drawing, you either specify a precise scale or fit the image to the output size. You specify a scale with either a standard or custom plot scale.
A standard scale is used when the UseStandardScale property is set to TRUE. The actual scale at which the plot will be scaled to can be queried with the StdScale property.
A custom scale is used when the UseStandardScale property is set to FALSE. The custom scale at which the plot will be scaled to can be queried with the CustomPrintScale property.
When reviewing an early draft view, a precise scale is not always important. You can set the StdScaleType property to a value of ScaleToFit defined by the StdScaleType enum to plot the layout at the largest possible size that fits the output size.