The free smells signs at Jimmy Johns is basically a joke sign that says they provide you with free smells before you even walk into the store.
The smells from Jimmy Johns cooking are so strong that they make their way through the building even without opening the door and then you smell them.
I used to work in a building next door to a Jimmy Johns that shared the same wall and when they cooked food I could easily smell those cooking smells.
Jimmy Johns food is also great and the smells will likely attract you to them and make you want to order which it did for me.
I used to order lunch at Jimmy Johns when I worked next door.