Just take whatever they mentioned in the letter. They will most probably not even see it. But they will ask, if you got it with you.
If your appointment is for the morning, go at least an hour early. It takes a long time to get inside the building.
If your appointment is in the afternoon, you can arrive 10-15 mins earlier.
I had to wait two hours to get my EAD. No problems, no hassle, just had to sit and wait. Take some reading material or something to do.
Regards,
AmIinTrouble