[State -3, NotHitBy]
type = NotHitBy
trigger1 = 1
value = ,AT
time = 1

This is the attribute of the attack. It is used to determine if the attack can hit P2. In this case, it is a Standing Normal Attack.

attr has the format attr = arg1, arg2, where:

    arg1 is either S, C or A. Similar to statetype for the StateDef, this says whether the attack is a standing, crouching, or aerial attack.
    arg2 is a 2-character string. The first character is either N for "normal", S for "special", or H for "hyper" (or "super", as it is commonly known). The second character must be either A for "attack" (a normal hit attack), T for "throw", or P for projectile.