high-hopes, one can only wish
.
Dave Noble is correct, it's simply the fist character of the booking reference.
If you are on international flights,
click this AMADEUS Link and whack that
booking reference and
your Surname in and hit enter. It should show details of your booking.
If you click the black
+'s in little boxes with
Orange background; you will get more details, including any allocated seating. Click this and you may even get a seatmap and you can see where you have been put.