According to WP newsletter (which I paid $10 for; they don't
have change)
The serial number is to ensure that everyone has only one vote and
votes are accounted for. Apparently, all political parties will get
a CD will the details of all eligible voters and their serial
number.
Once the ballots are counted, the ballot cards are destroyed
immediately under the supervision of the parties involve and the
election committee. No one is allowed to review the ballot
cards.
Your vote is secret and safe - WP 
