At an all-way stop, when it comes to right-of-way, "first in, first out" means .

Explanation:

"Yield to any road users who arrived before you",

We can apply this to the road situation. When we are in a situation  of a four-way stop with no traffic light, the first car that arrives at the intersection has "the right of way" or he has the priority to go first. The location of the cars or their direction don't have any importance; the car that arrives first at the intersection has the priority to go first ( first in, first out).