On the contrary, positive depth has always been away from the viewer and negative is towards. =)
Positive depths appear more "on top". Try -100.
"In GameMaker:Studio a low depth (of negative numbers like -1000) means that the instance will be drawn "closer" to the player and on top of all instances with a lower depth, while a high depth (of positive numbers like 1000) means that the instance will be drawn "further away" from the player and beneath those instances that have a lower depth."