I think instead of 'flight numbers' he means 'flight date'.

As far as flying standby goes, I've read that for some extremely restricte tickets (ones bought from priceline, for example), you can't fly standby. However, for just about everything else (my experience being with Delta), it's not a problem.
I flew from PHL to HNL in October on FF tickets on Delta, and when trying to change to get a better flight, they were the ones who told me about standby as being an option. Also, during my 12 segment segment-run on DL in December, we had no problems flying standby, and all of the flights were with electronic tickets. The agent just wanted to know what flight we were originally booked on, so he could see if the standby flight was valid, and update the records.

Jeff