I know that a low AC is better but I have a Chainmail+1
Stats:
Armor Class: 4 (2 vs. slashing, 6 vs. crushing)

and I don't understand how the (2 vs. slashing, 6 vs. crushing) affects the character.


Is it like:
Monster uses a slashing weapon = armor acts like AC2

Monster uses crushing weapon= armor acts like AC6

or like

Monster uses a slashing weapon = armor acts like AC4-2 (acts like AC2)

Monster uses crushing weapon= armor acts like AC4-6 (acts like AC-4)