This slash went uncalled in the game, but thanks to video, the NHL Department of Player Safety was able to crackdown on the slash.
At first look, it seems that the slash may be harmless and didn't have much intent behind it, but remember that part of the arm is all bone and skin, has no padding, and the stick is solid material. Even a small slash is going to hurt a good amount, and this was definitely more than just a small slash.