I think when an answer migrated, reputation deduction depends on the number of upvotes on that answer. One of my answers was migrated from Web Applications to Super User site. Before migration my reputation was 1446 on Web Applications. But once it got migrated, my reputation changed to 1430. Total deduction is 16 reputation. But on Super User my reputation increment is only 10 which is correct because answer has only one upvote.
My question is can anyone explain about that other 6 reputation?