Negative Damage Bug (Visual Only)

I just played a game where I was randomly dealing negative damage to some minions at exactly -2,147,483,648. When it occurred it would consistently happen to the same creep until death with Garen's E only, as far as I noticed. The other creeps took normal damage. This would happen to one creep per wave or every creep sometimes. The Zed I was fighting took the same damage bug from ignite. This was entirely visual as the actual damage was dealt despite the numbers appearing so it isn't anything super game breaking.