Each stealing event = 5 neg karma.
example: a red footlocker containing 10 .308 ammo, 5 scrap metal, 1 teddy bear.
open box press take all button = -5 karma
open box, take 1 scrap metal, close box reopen box take teddy bear = -10 karma
it's all based on the opening of the box. It's the act of going in the box and taking something that gives the -5 karma hit. on consoles this is a good way to lower karma or stay neutral as you can take a stack of items one by one and get more negative karma.