What do you mean, fortune telling is grandma?

What exactly does grandma mean? I'm confused! I come from the south.

In the north, grandma is usually my mother's mother, which means grandma, while in some places in the south, grandma and aunt in the north mean the same thing! So I call my aunt's son, and my cousin is right! It's just caused by regional and cultural differences! Grandma is generally called in the south, and there is no habit of calling grandma!