How does game order advancement criteria?

I have an advancement checking for two variations of an item in the players mainhand and offhand. I then execute as @s with each advancement criteria. It always only gives one output and it usually preferes the mainhand except when the offhand is "no_gem" and the mainhand is "gem" then it outputs the offhand gem all of a sudden.
Is there any logic to how it chooses criteria when multiple are met?