I am creating an export for Meta Shop, I need to export the value for the specific "Size" however I'm not sure how to export just that specification.
Use this bit of code where you want to write out the value of the specific:
[%item_specifics id:'[@sku@]'; name:'Size'%][%param *body%][@itmspecval_value@][%/param%][%/item_specifics%]
Docs for that tag are here:
https://developers.maropost.com/documentation/neto-designer-documentation/b-se-tag-library/function-tags/product-information/item_specifics/