The EMD was a new thing to me having never booked with Emirates before. I thought everything would be linked by Booking Reference but it seems their systems are more by EMD number. EMD numbers start 176. I expected just one of these or one person passenger but we had lots, I think as when we bought flights the seats did not go through and then we had separate transactions for seats. Though best thing is to open every pdf for everything like each seat, each flight and put what it says is that emd number on the form. Online it says it stands for Emirates Electronic Miscellaneous Document (EMD).
Though someone else may know more than me. I have just muddled my way through this.