The first time you add a feature, you specify a style from the Select Style dialog box. When you add another feature of the same type, it uses the same style by default, but you can change it.
As you sketch, you can enter a specific value or drag to the desired size. Information about the feature size appears and updates. Values use the current unit of measure. You can move the value box by dragging it to a different location.
You can undo almost any change in a proposal or model that you made in the current session. Press Ctrl + Z to undo.