dear friend
case number plus the abbreviated prefix of your region(continent) is an identifier that indicates how many people are before or/and after you in your region.
for example supposed that some body's case number is 2008AS5268, it means:
1. he is winner of the year 2008
2. he is from Asia
3. his rank is 5268 out of for example 11000 for the Asia region.
now is the turn of importance of the numbers:
you know that every year about 50000 lottery visas granted to winners participants, but the point is the KCC(Kentucky Consular Center) announces more than 50000 people(for example this year they announced about 80000) each year in case, this extras are in reserve.
one important thing is if they've written the word "CONGRATULATIONS" at the top of your notification letter it is a good reason that you are not among the reserves and you have a chance to get the visa.
if you write your case number here,many experienced friends like Barbara-Catseyes-Anahit and ... can help & guide you more but be sure to write your last 2 digits of your number this way 2008AS52XX.
hope it helps
good luck