Merged server rewards are calculated based on the difference between the first servers and last servers opening date. I.E. servers 1,2,3,4 are merged, rewards are based on server 1 and 2’s opening date. BUT, this feature was not supposed to go online and we consider it as bug. Therefore, if there are differences in calculations, it is because of the current situation.
Coupons are based on who's older and newer server .. On our case S584 is the oldest of the 4 servers (S584 -> S591 -> S614 -> S674) and S674 players got 2k cps ..