A/V/N+다(고) 치고 indicates that the following situation is hypothetical future. It roughly translates to 'let's say/suppose/pretend/assume that'. The sentence is sometimes preceded by 설령, 가령 to emphasise the hypothetical nature of the situation.
첫차를 탄다고 쳐도 점심까지는 못 가요.
Let's suppose that I took the first train -- I still wouldn't be able to get there lunchtime.
별장 요금을 여유가 있다고 치고, 별장까지 어떻게 갈 거예요?
Even if we suppose that you can afford to stay at the villa, how are you going to get there?
그 말이 맞다고 쳐요. 한 번 애기가 들어보자.
Let's assume that you're right. Let's hear him out.
그들이 결혼하게 된다고 쳐요...
Suppose they end up getting married...
가령 저한테 복수를 하려 한다고 쳐요...
Let's say he tries to get revenge on me...
그 말은 안 들었다 치고 우리 다른 애기를 합시다...
Let's pretend we didn't hear that and talk about something else...
설령 동료들이 반대를 한다고 쳐요. 그때는 어떡할 거에요?
Let's suppose that your colleagues oppose you. What will you do then?
앞 사람들이 많다 치고 발표 연습해 보세요.
Practice your presentation as if (supposing) there were lots of people in front of you.
편지를 등기우편으로 보낸다 치고 아직 다음 주까지 못 도착할 거예요.
Even if you send the letter by registered mail, it still won't arrive until next week.
그것은 그렇다 치고 그 사람이 저에게 무례했다고 아직 생각해요.
That being said (let's say it's like that), I still think that he was rude to me.
When used with 그렇다, the situation is already known to both speaker and listener:
그것은 그렇다 치고 그 사람이 저에게 무례했다고 아직 생각해요.
That being said (let's say it's like that), I still think that he was rude to me.