You'd be right if the Finance System worked in the conventional sense - but this is the DEFENSE Accounting and Finance System. They actually run cycles outside of paydays whaich makes it kinda wierd. For instance, for someone to start gettng benefits, for the first through the fifteenth, they must be included in the cycle ending on the eighth... It's my understanding that they run "cycles" every few days, or maybe once a week (I've never really wanted to know the exact timeframe so I've never asked).
The bonus is paid out 9k, 9k, and 2k all less tazes. This is because the finance system will not allow for a check over 10k. I've seen it take anywhere from 5 days to four weeks to complete the payment depending on where in the cycle the first stipend payment was made.