In the episode "Sins of the Father", Riker says that Kurn has the crew on his toes. I get that. But then Geordi says "And then some" which is obviously a response, but is that supposed to be an insult to Kurn?
KURN: I find the constraints a bit difficult to conform to. Just a short while ago, I had to stop myself from killing Commander Riker. I believe he was trying to communicate the crew's sense of discomfort with my style of command. Under different circumstances, I would consider that a challenge to my authority.
PICARD: One of the aims of the exchange programme, Commander, is for all of us to learn tolerance. As for my crew, it may be healthy to shake up the status quo occasionally.
RIKER: The Commander certainly appears to have the crew on its toes
LAFORGE: And then some. No offence, sir.
"And then some" as an English phrase simply means "that and more" with an implication that it's too much. Geordi is insinuating that Kurn's style of command not only had the crew ready, but also anxious, which is not necessarily a good thing. In this case, the death threats are part of what is putting people over the edge.