For example imagine that I have these 2 token variables:
page.margin = 16
icon.padding = 10
and that I have a component that contains an icon with the padding. To ensure the icon aligns vertically I need my component to have a margin of 6, but only because the icon already contains 10 padding.
Therefore, to make my design using tokens I need to specify the padding as: page.margin - icon.padding = 6.
I do not want to use the value 6 directly as then when tokens are updated the design will not be.
This is related to Using expression as a variable's value but not the same.
To support tokens for measurements this is essential.