You aren’t entitled to anything but delta is pretty good about tossing out miles, fill out the form on line, keep it short and to the point, my flight was five hours late arriving, delay was mechanical, I would like xxx number of miles, if you booked the flight thru corp travel and work at a large firm adding in I missed an important dinner is fine otherwise I wouldn’t bother, in the end you want the key words 5 hours late, mechanical and number of miles