In what sense do non-restrictive phrases limit meaning?
It's well known that non-restrictive phrases are inessential to the meaning of the sentence because they
do not limit the reference of a word or phrase.
But in this example, the non-restrictive word 'Susan' (between parenthetical commas) seems to add information that limits meaning.
My sister, Susan, likes to shop
'Susan' is an appositive that renames "my sister" as "Susan", and says I only have one sister (Susan). It adds information that limits "my sister" to 'Susan': surely that means that it limits meaning, as well as not limiting the referent?
What is the difference between the "reference" that isn't limited and the meaning that is?