You can also select a part in the tree view, and it will show in the part and preview windows.
Substitution Values
Properties with $'s are substitution values. $ScrollBarWidth$ is one of many substitution values.
Right below the top value of the tree are the substitution values section for each font.
Rather then have three sets of properties for each font type, we have substitution values for each size.
For example, take $ScrollBarWidth$.
Blue\Values\General\Sysmetrics :
The $$'s show that the value is located under Blue\Normal\Substitution, Blue\LargeFonts\Substitution, and Blue\ExtraLarge\Substitution
Blue\Normal\Substitution
Blue\LargeFonts\Substitution
When normal fonts is used, the scrollbar width will be 17, when Large Fonts are used, the scrollbar width will be 19.