One of those stun rounds would have hit Fitz in the face if the glass wasn't there. Hard enough to score the glass! That CAN'T be healthy.
Yeah, that was why I discounted the talk about it being non-lethal. But upon rewatching it, I could see that the gun had the blue markings. If I'd been showrunner and wanted the rounds really to be night-night rounds, I wouldn't make it do that to the glass, but whatev.