You can edit the dimensions of a wall opening by changing the properties on the opening’s Size property page.
To edit the size of a wall opening:
Select the opening whose properties you want to change.
Right-click and select Properties, or select Edit > Modify Elements > Properties.
In the Properties area, edit the dimensions of the opening. Dimensions vary according to the shape of the opening.
Click OK.
Tip: If you want the bottom of your opening to be level with the floor, change the height of opening to match the Head Height of the building location it is inserted on. Alternatively you can lower the opening using the Elevate tool.