Yeah, a single is just one rep. I would listen to pauls advice, he deadlifts more than I do by a long way. Doing singles only works for me on deadlifts, I burn out horribly if I try it on any other exercise, so its probably not recommendable especially when starting out. Its an experiment you can try when your CNS is used to the massive extra strain that deadlifts put upon your body perhaps.
Its worth noting that Ive always been told that even when you are doing reps of deadlifts, you do them as "A set of singles" rather than as a normal set. Basically, set your feet, do the lift, put down the weight, step away. Reset your feet, lift again, step away. Rinse and repeat. Rather than keeping your feet in the same place and just raising and lowering the bar.
I think its to stop sloppiness from creeping in to the technique, make you concentrate on the setup, and also to stop you from attempting to build a concentric portion into the lift by attempting to control the weight on the way down, which you do not need to do.
I have seen a very impressive video of a guy called Steve repping out 700lbs for 7 reps without moving his feet though.
Paul, if I could have hit 400lbs, I would have considered myself to be fairly strong. If I tried even 300 now, Id probably snap my back in two, let alone not being able to hold on to the weight. Confounded lift gets in the way of lifting far too often.