What does the symbol that looks like a monster movement symbol on gate tokens mean? Or what is it used for?

Predator said:

In the core rules, pag 18, there is an entire paragraph answering your question: "Monsters and closing gates"

When a gate is closed, all monsters in Arkham, the Sky, and the Outskirts that have the same dimension symbol (see “Monster Movement,” page 10) as the closed or sealed gate are removed from the board and returned to the cup. A monster’s dimension symbol is printed in the lower-right corner of the marker’s movement side

And there I spent all the time looking for ANATOMY of the gate marker….oops.