Departing Miami in a B757 one day we were given a clearance by departure to climb to 8,000 ft. I read the clearance back and told the FO, that is strange, arrivals descend to 8 and departures climb to 7. The FO said we are cleared to 8. Out of 6,000 I saw opposite direction traffic approaching us at 8,000. I told the FO do not go above 7,000 until we clear traffic. I called departure and said verify we are cleared to 8,000 on our climb. He said no, you are cleared to 7,000 ft. I said I read back 8,000, my FO verified your clearance but we had traffic on our TCAS so stayed at 7,000.
It was no big deal because we knew something was wrong but a new person leaving MIA wouldn't know standard procedures. Everybody makes a mistake now and then, just cover your butt when things don't look right.