How can we interpret the meaning of the total effects for a completely discrete variable (e.g. a categorical variable with no numerical values)?

I am aware of this page

but I don't understand how it applies to categorical variables.
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All the states (numerical or symbolic) have an associated numerical value. 
For symbolic variables, if the user did not manually define any values (Node Editor | Values tab), the state value is just its rank.

Hope this clarifies
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