I am looking for train leaving on Friday.
Sure! What is your destination and departure preference? 
I will be going to the lovely village of Kings Lynn, it be be after I get out of work, so I need to leave after 21:30.  
There is a 12:11 is that is not too soon for you to leave.  
I said 21:30. Try again.
I'm sorry I misunderstood you. There are 2 trains leaving after 21:30. TR0394 leaves at 22:11 and TR2311 at 23:11 both depart from cambridge.