Yeah, the wiki can't be trusted. I found this earlier on Kenny's page:
If Lee agrees to leave Kenny, he will give Kenny bullets. As he is leaving, Lee hears Kenny fire off two shots, one at Ben and one at himself, saving them both the pain. This can only happen if Ben is saved in Episode 4.
There was obviously one
bullet left from the gun that Kenny took from the couple, since the group ran out of bullets from shooting walkers in the mansion =.=