Symbolic proportion is when you apply different thing to describe what something is to someone means. Symbolic proportion is the likely unbalanced connection among things within a piece. Others describe symbolic proportion as the production of an ostensibly excessive attachment in order to communicate the essence of something.
I could say that it means you use another item to explain what it means to the audience. Symbolic proportion is the apparent disproportionate relationship between objects within a piece. Others define symbolic proportion as the creation of an apparently disproportionate relationship in order to convey the importance of something.