Why were some users awarded a large reputation bounty during the migration to Confluence Questions?

[Migration Bot 9000]

Now that Atlassian Answers is running on a system powered by Confluence Questions, many users (especially those with very high amounts of reputation), show that a large bounty was awarded to them on the date of the migration. Why did this happen? Why do some users get a bounty and others not, and why are the amounts different?

[Migration Bot 9000 · Accepted solution]

We implemented a 'one-off' bounty award during the migration from the legacy Answers system to Confluence Questions. Because karma/reputation is awarded differently in Confluence Questions than in the old system, some users had drastically lower reputation totals in the new system than the old one. In order to counteract people feeling "cheated" by this loss, we bumped everyone's reputation total back up to where it was before the migration.