Each style is like a list of formatting differences from its parent style. For example if a style has the "bold" property, then "bold" is added to the parent. Each formatting item has the following possible states:
On The formatting property is added. E.g. Bold-On
Off The formatting property is removed. E.g. Bold-Off
A Number This number applies to items like scaling, or font point size. E.g. scaling = 120%.
Font Name This overrides the font used.
No Change The style has no effect on the formatting property. It inherits the properties of the parent style.